SB    E77 


HHMHMHI 


nmpr   School   Of 


LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA 

GIFT  OR 


Received 
Accession  No.~~*7'.       Class  No 


GINN  &  CO, 
g 27-3 81  Sansome  Street, 


INTRODUCTION 


TO 


CHEMICAL   SCIENCE. 


BY 


R.   P.   WILLIAMS,   A.M., 

INSTRUCTOR  IN  CHEMISTRY,  ENGLISH  HIGH  SCHOOL,  BOSTON, 
AND  AUTHOR  OF  "  LABORATORY  MANUAL." 


BOSTON,   U.S.A.: 

GINN  &  COMPANY,  PUBLISHERS. 
1894. 


6  3  6-3-7 

Entered  according  to  Act  of  Congress,  in  the  year  1887,  by 

R.  P.  WILLIAMS, 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


TYPOGRAPHY  BY  J.  S.  GUSHING  &  Co.,  BOSTON. 


PRESSWORK  BY  GINN  &  Co.,  BOSTON. 


PREFACE. 


rpHE  object  held  constantly  in  view  in  writing  this  book  has  been 
to  prepare  a  suitable  text-book  in  Chemistry  for  the  average 
High  School,  —  one  that  shall  be  simple,  practical,  experimental,  and 
inductive,  rather  than  a  cyclopaedia  of  chemical  information. 

For  the  accomplishment  of  this  purpose  the  author  has  endeavored 
to  omit  superfluous  matter,  and  give  only  the  most  useful  and  inter- 
esting experiments,  facts  and  theories. 

In  calling  attention,  by  questions  and  otherwise,  to  the  more  im- 
portant phenomena  to  be  observed  and  facts  to  be  learned,  the  best 
features  of  the  inductive  system  have  been  utilized.  Especially  is  the 
writing  of  equations,  which  constitute  the  multum  in  parvo  of  chem- 
ical knowledge,  insisted  upon.  As  soon  as  the  pupil  has  become 
imbued  with  the  spirit  and  meaning  of  chemical  equations,  he  need 
have  little  fear  of  failing  to  understand  the  rest.  To  this  end 
Chapters  IX.,  XL,  and  XVI.  should  be  studied  with  great  care. 
In  the  early  stages  of  the  work  the  equations  may  with  advantage 
be  memorized,  but  this  can  soon  be  discontinued.  Whenever  sym- 
bols are  employed,  pupils  should  be  required  to  give  the  correspond- 
ing chemical  names,  or,  better,  both  names  and  symbols. 

The  classification  of  chemical  substances  into  acids,  bases  and 
salts,  and  the  distinctions  and  analogies  between  each  of  these  classes, 
have  been  brought  into  especial  prominence.  The  general  relation- 
ship between  the  three  classes,  and  the  general  principles  prevail- 
ing in  the  preparation  of  each,  must  be  fully  understood  before 
aught  but  the  merest  smattering  of  chemical  science  can  be  known. 


v  PREFACE. 

Chapters  XV.-XXI.  should  be  mastered  as  a  key  to  the  subsequent 
parts  of  the  book. 

The  mathematical  and  theoretical  parts  of  Chemistry  it  has  been 
thought  best  to  intersperse  throughout  the  book,  placing  each  where  it 
seemed  to  be  especially  needed;  in  this  way,  it  is  hoped  that  the 
tedium  whjch  pupils  find  in  studying  consecutively  many  chapters 
of  theories  will  be  avoided,  and  that  the  arrangement  will  give  an 
occasional  change  from  the  discussion  of  facts  and  experiments  to 
that  of  principles.  In  these  chapters  additional  questions  should  be 
given,  and  the  pupil  should  be  particularly  encouraged  to  make  new 
problems  of  his  own,  and  to  solve  them. 

It  is  needless  to  say  that  this  treatise  is  primarily  designed  to 
be  used  in  connection  with  a  laboratory.  Like  all  other  text-books 
on  the  subject,  it  can  be  studied  without  such  an  accessory ;  but  the 
author  attaches  very  little  value  to  the  study  of  Chemistry  without 
experimental  work.  The  required  apparatus  and  chemicals  involve 
but  little  expense,  and  the  directions  for  experimentation  are  the 
result  of  several  years'  experience  with  classes  as  large  as  are  to  be 
found  in  the  laboratory  of  any  school  or  college  in  the  country. 
During  the  present  year  the  author  personally  supervises  the  work 
of  more  than  180  different  pupils  in  chemistry.  This  enables 
him  not  only  to  assure  himself  that  the  experiments  of  the  book  are 
practical,  but  that  the  directions  for  performing  them  are  ample. 
It  is  found  advisable  to  perform  most  of  the  experiments,  with  full 
explanation,  in  presence  of  the  class,  before  requiring  the  pupils  either 
to  do  the  work  or  to  recite  the  lesson.  In  the  laboratory  each  pupil  has 
a  locker  under  his  table,  furnished  with  apparatus,  as  specified  in  the 
Appendix.  Each  has  also  the  author's  "  Laboratory  Manual,"  which 
contains  on  every  left-hand  page  full  directions  for  an  experiment,  with 
observations  to  be  made,  etc.  The  right-hand  page  is  blank,  and  on 
that  the  pupil  makes  a  record  of  his  work.  These  notes  are  examined  at 
the  time,  or  subsequently,  by  the  teacher,  and  the  pupil  is  not  allowed 
to  take  the  book  from  the  laboratory ;  nor  can  he  use  any  other  book 


PREFACE.  V 

on  Chemistry  while  experimenting.     By  this  means  he  learns  to  make 
his  own  observations  and  inferences. 

For  the  benefit  of  the  science  and  the  added  interest  in  the  study,  it 
is  earnestly  recommended  that  teachers  encourage  pupils  to  fit  up  labo- 
ratories of  their  own  at  home.  This  need  not  at  first  entail  a  large 
outlay.  A  small  attic  room  with  running  water,  a  very  few  chemicals, 
and  a  little  apparatus,  are  enough  to  begin  with ;  these  can  be  added 
to  from  time  to  time,  as  new  material  is  wanted.  In  this  way  the 
student  will  find  his  love  for  science  growing  apace. 

While  endeavoring,  by  securing  an  able  corps  of  critics,  and  in  all 
other  ways  possible,  to  reduce  errors  to  a  minimum,  the  author 
disclaims  any  pretensions  to  a  work  entirely  free  from  mistakes, 
holding  himself  alone  responsible  for  any  shortcomings,  and  trusting 
to  the  leniency  of  teachers  and  critics. 

The  manuscript  has  been  read  by  Prof.  Henry  Carmichael,  Ph.D., 
of  Boston,  and  to  his  broad  and  accurate  scholarship,  as  well  as  to 
his  deep  personal  interest  in  the  work,  the  author  is  indebted  for 
much  valuable  and  original  matter.  The  following  persons  have  gen- 
erously read  the  proof,  as  a  whole  or  in  part,  and  made  suggestions  re- 
garding it,  and  to  them  the  author  would  return  his  thanks,  as  well  as 
acknowledge  his  obligation  :  Prof.  E.  J.  Bartlett,  Dartmouth  College, 
N.H. ;  Prof.  F.  C.  Robinson,  Bowdoin  College,  Me. ;  Prof.  H.  S.  Car- 
hart,  Michigan  University;  Prof.  B.  D.  Halsted,  Iowa  Agricultural 
College ;  Prof.  W.  T.  Sedgwick,  Institute  of  Technology,  Boston  ;  Pres. 
M.  E.  Wadsworth,  Michigan  Mining  School;  Prof.  George  Hunting- 
ton,  Carleton  College,  Minn.;  Prof.  Joseph  Torrey,  Iowa  College; 
Mr.  C.  J.  Lincoln,  East  Boston  High  School;  Mr.  W.  H.  Sylvester, 
English  High  School,  Boston ;  Mr.  F.  W.  Gilley,  Chelsea,  Mass.,  High 
School ;  the  late  D.  S.  Lewis,  Chemist  of  the  Boston  Gas  Works,  and 
others. 

R.  P.  W. 

BOSTON,  January  3,  1888. 


tJFIVEESITY 


TABLE    OF    CONTENTS. 


CHAPTER   I. 

THE    METRIC    SYSTEM. 

PAGE 

Length. — Volume. — Weight 1 

CHAPTER   II. 
DIVISIBILITY    OF    MATTER. 

Mass.  —  Molecule.  —  Atom.  —  Element.  —  Compound.  —  Mixture.  — 

Analysis.  —  Synthesis.  —  Metathesis.  —  Chemism     .....        3 

CHAPTER   III. 

MOLECULES    AND    ATOMS. 
Synthesis     .    „    ....    ,  -.    .    .    , 8 

CHAPTER   IV. 

ELEMENTS    AND    BINARIES. 

Symbols.  —  Names.  —  Coefficients.  —  Exponents.  —  Table  of  ele- 
ments  10 

CHAPTER  V. 

MANIPULATION. 

To  prepare  and  cut  glass,  etc.  .     ,    ; 14 

CHAPTER  VI. 
OXYGEN. 

Preparation.  —  Properties.  —  Combustion   of   carbon ;     sulphur ; 

phosphorus ;  iron 17 


Vlll  TABLE   OF    CONTENTS. 

CHAPTER   VII. 
NITROGEN. 

PAGE 

Separation.  —  Properties 22 

CHAPTER  VIII. 
HYDROGEN. 

Preparation.  —  Properties.  —  Combustion.  —  Oxy-hydrogen  blow- 
pipe   24 

CHAPTER   IX. 

UNION    BY    WEIGHT. 

Meaning  of  equations.  —  Problems ....      29 

CHAPTER  X. 
CARBON. 

Preparation.  —  Allotropic  forms  :  diamond,  graphite,  amorphous 
carbon,  coke,  mineral  coal.  —  Carbon  a  reducing  agent,  a  de- 
colorizer,  disinfectant,  absorber  of  gases 32 

CHAPTER  XI. 

VALENCE. 
Poles  of  attraction.  —  Radicals     .    .- 38 

CHAPTER   XII. 
ELECTRO-CHEMICAL    RELATION    OF    ELEMENTS. 

Deposition  of  silver;  copper;  lead.  —  Table  of  metals  and  non- 
metals,  and  discussion  of  their  differences 41 

CHAPTER  XIII. 

ELECTROLYSIS. 

Decomposition  of  water  and  of  salts.  —  Conclusions 44 


TABLE   OF   CONTENTS.  IX 

CHAPTER   XIV. 

UNION    BY    VOLUME. 

PAGE 

Avogadro's  law  and  its  applications 46 

CHAPTER  XV. 

ACIDS    AND    BASES. 

Characteristics  of  acids  and  bases.  —  Anhydrides.  —  Naming  of 

acids.  —  Alkalies 49 

CHAPTER  XVI. 
SALTS. 

Preparation  from  acids  and  bases.  —  Naming  of  salts.  —  Occur- 
rence  53 

CHAPTER  XVII. 
CHLORHYDRIC    ACID. 

Preparation  and  tests.  —  Bromhydric,  iodihydric,  and  fluorhydric 

acids.  —  Etching  glass 56 

CHAPTER  XVIII. 
NITRIC    ACID. 

Preparation,  properties,  tests,  and  uses.  —  Aqua  regia:  prepara- 
tion and  action ;    , 60 

CHAPTER  XIX. 
SULPHURIC    ACID. 

Preparation,  tests,  manufacture,  and  importance.  —  Fuming  sul- 
phuric acid 63 

CHAPTER  XX. 
AMMONIUM    HYDRATE. 

Preparation  of  bases.  —  Formation,  preparation,  tests,  and  uses 

of  ammonia  .  67 


X  TABLE  OF  CONTENTS. 

CHAPTER  XXI. 
SODIUM    HYDRATE. 

PAGE 

Preparation  and  properties.  —  Potassium  hydrate   and   calcium 

hydrate • G9 

CHAPTER  XXII. 

OXIDES    OF    NITROGEN. 

Nitrogen  monoxide,  dioxide,  trioxide,  tetroxide,  pentoxide  .         .      72 

CHAPTER  XXIII. 

LAWS  OF  DEFINITE  AND   OF  MULTIPLE  PROPORTION, 
and  their  application 75 

CHAPTER  XXIV. 

CARBON    PROTOXIDE 
and  water  gas 77 

CHAPTER  XXV. 
CARBON    DIOXIDE. 

Preparation  and  tests.  —  Oxidation  in  the  human  system.  —  Oxi- 
dation in  water.  —  Deoxidation  in  plants 79 

CHAPTER  XXVI. 
OZONE. 

Description,  preparation,  and  test 84 

CHAPTER  XXVII. 

CHEMISTRY    OF    THE   ATMOSPHERE. 
Constituents  of  the  air.  —  Air  a  mixture.  —  Water,  carbon  dioxide, 

and  other  ingredients  of  the  atmosphere     .",..«....      8G 

CHAPTER  XXVIII. 
THE    CHEMISTRY    OF   WATER. 

Distillation  of  water.  —  Three  states.  —  Pure  water,  sea-water, 

river- water,  spring- water ,    . 88 


TABLE   OF   CONTENTS.  XI 

CHAPTER  XXIX. 
THE    CHEMISTRY    OF    FLAME. 

PAGE 

Candle  flame.  —  Bunsen  flame.  —  Light  and  heat.  —  Temperature 
of  combustion.  —  Oxidizing  and  reducing  flames.  —  Combusti- 
ble and  supporter.  —  Explosive  mixture  of  gases.  —  Generali- 
zations   91 

CHAPTER  XXX. 
CHLORINE. 

Preparation.  —  Chlorine  water.  —  Bleaching  properties.  —  Disin- 
fecting power.  —  A  supporter  of  combustion.  —  Sources  and 
uses .  .  . 98 

CHAPTER  XXXI. 

BROMINE. 
Preparation.  —  Tests.  —  Description.  —  Uses 101 

CHAPTER  XXXII. 
IODINE. 

Preparation.  —  Tests.  —  lodo-starch  paper.  —  Occurrence.  —  Uses. 

—  Fluorine    .   /.  '.  ".   V  .-.    .    .    .    .    .    .; 103 

CHAPTER  XXXIII. 

THE    HALOGENS. 
Comparison.  —  Acids,  oxides,  and  salts 106 

CHAPTER   XXXIV. 
VAPOR    DENSITY    AND    MOLECULAR   WEIGHT. 

Gaseous  weights  and  volumes.  —  Vapor  density  defined.  —  Vapor 

density  of  oxygen .     .    .  ' . 108 

CHAPTER  XXXV. 
ATOMIC    WEIGHT. 

Definition.  —  Atomic  weight  of  oxygen.  —  Molecular  symbols.  — 

Molecular  and  atomic  volumes ,  111 


Xll  TABLE   OF    CONTENTS. 

CHAPTER  XXXVI. 
DIFFUSION    AND    CONDENSATION    OF    GASES. 

PAGE 

Diffusion  of  gases.  —  Law  of  diffusion.  —  Cause.  —  Liquefaction 

and  solidification  of  gases 114 

CHAPTER  XXXVII. 
SULPHUR. 

Separation.  —  Crystals  from  fusion.  —  Allotropy.  —  Solution.  — 
Theory  of  Allotropy. —  Occurrence  and  purification.  —  Uses. 

—  Sulphur  dioxide 116 

CHAPTER  XXXVIII. 
HYDROGEN    SULPHIDE. 

Preparation.  —  Tests.  —  Combustion.  —  Uses.  —  An  analyzer  of 

metals.  —  Occurrence  and  properties *    ...     120 

CHAPTER  XXXIX. 
PHOSPHORUS. 

Solution  and  combustion.  —  Combustion  under  water.  —  Occur- 
rence. —  Sources.  —  Preparation  of  phosphates  and  phos- 
phorus. —  Properties.  —  Uses.  —  Matches.  —  Red  phosphorus. 

—  Phosphene     ....,..,. 122 

CHAPTER  XL. 

ARSENIC. 

Separation.  —  Tests.  —  Expert  analysis.  —  Properties  and  occur- 
rence.—  Atomic  volume.  —  Uses  of  arsenic  trioxide.  .  .  .  126 

CHAPTER  XLL 
SILICON,   SILICA,   AND    SILICATES. 

Comparison  of  silicon  and  carbon.  —  Silica.  —  Silicates.  —  Forma- 
tion of  silica .  ,  .  .  .  ,  130 


TABLE   OF   CONTENTS.  Xlll 

CHAPTER  XLII. 
GLASS    AND    POTTERY. 

PAGE 

Glass  an  artificial  silicate.  —  Manufacture.  —  Importance.  —  Porce- 
lain and  pottery .  .  .  .  ^  .7-  .  .  .  .  .  ,  ...  .  .  .  .  132 

CHAPTER   XLIII. 
METALS    AND    THEIR    ALLOYS. 

Comparison  of  metals  and  non-metals.  —  Alloys.  —  Low  fusibility. 

—  Amalgams.     .....    .    .  ^v 135 

CHAPTER  XLIV. 
SODIUM    AND    ITS    COMPOUNDS. 

Order  of  derivation.  —  Occurrence  and  preparation  of  sodium 
chloride;  uses.  —  Sodium  sulphate  :  manufacture  and  uses. 

—  Sodium  carbonate:   occurrence,  manufacture,  and  uses.— 
Sodium  :  preparation  and  uses.  —  Sodium  hydrate  :  prepara- 
tion and  use.  —  Hydrogen  sodium  carbonate.  —  Sodium  nitrate,     138 

CHAPTER  XLV. 

POTASSIUM    AND    AMMONIUM. 

Occurrence  and  preparation  of  potassium.  —  Potassium  chlorate 

and  cyanide.  —  Gunpowder.  —  Ammonium  compounds  ...     143 

CHAPTER  XL VI. 
CALCIUM    COMPOUNDS. 

Calcium  carbonate.  —  Lime  and  its  uses.  —  Hard  water.  —  Forma- 
tion of  caves.  —  Calcium  sulphate  . 146 

CHAPTER  XLVIL 

MAGNESIUM,   ALUMINIUM,   AND    ZINC. 

Occurrence  and  preparation  of  magnesium.  —  Compounds  of  alu- 
minium :  reduction ;  properties,  and  uses.  —  Compounds,  uses, 
and  reduction  of  zinc  .,.,..., .  150 


XIV  TABLE   OP   CONTENTS. 

CHAPTER  XLVIIL 
IRON    AND    ITS    COMPOUNDS. 

PAGE 

Ores  of  iron.  —  Pig-iron.  —  Steel.  —  Wrought-iron.  —  Properties. 

—  Salts  of  iron.  —  Change  of  valence  and  of  color  ....     154 

CHAPTER  XLIX. 

LEAD    AND    TIN. 

Distribution  of  lead.  —  Poisonous  properties.  —  Some  lead  com- 
pounds.—  Tin 161 

CHAPTER  L. 
COPPER,   MERCURY,   AND    SILVER. 

Occurrence  and  uses  of  copper.  —  Compounds  and  uses  of  mer- 
cury.—  Occurrence,  reduction,  and  salts  of  silver 164 

CHAPTER  LI. 

PHOTOGRAPHY. 

Description 167 

CHAPTER  LII. 

PLATINUM    AND    GOLD. 

Methods  of  obtaining,  and  uses 169 

CHAPTER  LIII. 
CHEMISTRY    OP   ROCKS. 

Classification.  —  Composition.  —  Importance  of  siliceous  rocks.  — 
Soils.  —  Minerals.  —  The  earth's  interior.  —  Percentage  of  ele- 
ments   171 

CHAPTER  LIV. 
ORGANIC    CHEMISTRY. 

Comparison  of  organic  and  inorganic  compounds.  —  Molecular 
differences. —  Synthesis  of  organic  compounds.  —  Marsh-gas 


TABLE  OF  CONTENTS.  XV 

PAGE 

series.  —  Alcohols.  —  Ethers.  —  Other  substitution  products. 

—  Oleflnes  and  other  series  .         174 

CHAPTER  LV. 

ILLUMINATING    GAS. 

Source,  preparation,  purification,  and  composition.  —  Natural  gas,     180 

CHAPTER  LVI. 
ALCOHOL. 

Fermented  and  distilled  liquors.  —  Effect  on  the  system.  —  Affinity 

for  water.  —  Purity 184 

CHAPTER  LVII. 
OILS,   FATS,   AND    SOAPS. 

Sources  and  kinds  of  oils  and  fats.  —  Saponification.  —  Manufac- 
ture and  action  of  soap.—  Glycerin,  nitro-glycerin,  and  dyna- 
mite. —  Butter  and  oleomargarine 186 

CHAPTER  LVIII. 
CARBO-HYDRATES. 

Sugars. —  Glucose.  —  Starch. —  Cellulose.  —  Gun-cotton.  —  Dextrin. 

—  Zylonite     . 189 

CHAPTER  LIX. 
CHEMISTRY    OF    FERMENTATION. 

Ferments.  — Alcoholic,  acetic,  and  lactic  fermentation.  —  Putre- 
faction.—  Infectious  diseases 193 

CHAPTER  LX. 
CHEMISTRY   OF  LIFE. 

Growth  of  minerals  and  of  organic  life.  —  Food  of  plants  and  of 

man,  —  Conservation  pf  energy  and  of  matter  , 196 


XVI  TABLE  OF  CONTENTS. 

CHAPTER  LXL 
THEORIES. 

The  La  Place  theory.  —  Theory  of  evolution.  —  New  theory  of 

chemistry 199 

CHAPTER  LXII. 

GAS   VOLUMES   AND    WEIGHTS, 
Quantitative  experiments  with  oxygen  and  hydrogen.  —  Problems,    201 


CHAPTER   I. 


THE  METRIC  SYSTEM. 

1.  The  Metric  System  is  the  one  here  employed.     A 
sufficient  knowledge  of  it  for  use  in  the  study  of  this  book 
may  be  gained  by  means  of  the  following 
experiments,  which  should  be  performed  at 

the  outset  by  each  pupil. 

2.  Length. 

Experiment  1.  —  Note  the  length  of  10cm  (cen- 
timeters) on  a  metric  ruler,  as  shown  in  Figure  1.  Es- 
timate by  the  eye  alone  this  distance  on  the  cover  of 
a  book,  and  then  verify  the  result.  Do  the  same  on 
a  t.t.  (test-tube).  Try  this  several  times  on  different 
objects  till  you  can  carry  in  mind  a  tolerably  accu- 
rate idea  of  10cm.  About  how  many  inches  is  it  ? 

In  the  same  way  estimate  the  length  of  lcm,  veri- 
fying each  result.  How  does  this  compare  with  the 
distance  between  two  blue  lines  of  foolscap?  Meas- 
ure the  diameter  of  the  old  nickel  five-cent  piece. 

Next,  try  in  the  same  way  5cm.  Carry  each  result 
in  mind,  taking  such  notes  as  may  be  necessary. 

3.  Capacity. 

Experiment  2.  —  Into  a  graduate, 
shown  in  Figure  2,  holding  25  or  50CC 
(cubic  centimeters)  put  10CC  of  water ;  then 
pour  this  into  a  t.t.  Note,  without  mark- 
ing, what  proportion  of  the  latter  is  filled ; 
pour  out  the  water,  and  again  put  into 
the  t.t.  the  same  quantity  as  nearly  as  can 
Fig.  3.  be  estimated  by  the  eye.  Verify  the  re-  Fig.  1. 


2  WEIGHTS  AND  MEASURES. 

suit  by  pouring  the  water  back  into  the  graduate.  Repeat  several 
times  until  your  estimate  is  quite  accurate  with  a  t.t.  of  given  size. 
If  you  wish,  try  it  with  other  sizes.  Now  estimate  lcc  of  a  liquid  in  a 
similar  way.  Do  the  same  with  5CC. 

A  cubic  basin  10cm  on  a  side  holds  a  liter.  A  liter  contains  1,000CC.  If 
filled  with  water,  it  weighs,  under  standard  conditions,  1,000  grams.  Ver- 
ify by  measurement. 

4.  Weight. 

Experiment  3.  —  Put  a  small  piece  of  paper  on  each  pan  of  a  pair 
of  scales.  On  one  place  a  10g  (gram)  weight.  Balance  this  by  plac- 
ing fine  salt  on  the  other  pan.  Note  the  quantity  as  nearly  as  possible 
with  the  eye,  then  remove.  Now  put  on  the  paper  what  you  think  is 
10s  of  salt.  Verify  by  weighing.  Repeat,  as  before,  several  times. 
Weigh  1&,  and  estimate  as  before.  Can  Is  of  salt  be  piled  on  a  one- 
cent  coin  ?  Experiment  with  5s. 

5.  Re"sume".  —  Lengths   are   measured   in  centimeters, 
liquids  in  cubic  centimeters,  solids  in  grams.     In  cases 
where  it  is  not  convenient  to  measure  a  liquid  or  weigh 
a  solid,  the  estimates  above  will  be  near  enough  for  most 
experiments  herein  given.     Different  solids  of  the  same 
bulk  of  course  differ  in  weight,  but  for  one  gram  what  can 
be  piled  on  a  one-cent  piece  may  be  called  a  sufficiently 
close  estimate.     The  distance  between  two  lines  of  fools- 
cap is  very  nearly  a  centimeter.     A  cubic  centimeter  is 
seen  in  Figure  1.     Temperatures  are  recorded  in  the  cen- 
tigrade scale. 


CHAPTER  II. 
WHAT  CHEMISTRY  IS. 


6.    Divisibility  of  Matter. 

Experiment  4.  —  Examine  a  few  crystals  of  sugar,  and  crush 
them  with  the  fingers.  Grind  them  as  fine  as  convenient,  and  ex- 
amine with  a  lens.  They  are  still  capable  of 
division.  Put  3s  of  sugar  into  a  t.t.,  pour 
over  it  5CC  of  water,  shake  well,  boil  for  a 
minute,  holding  the  t.t.  obliquely  in  the  flame, 
using  for  the  purpose  a  pair  of  wooden  nip- 
pers (Fig.  3).  If  the  sugar  does  not  dis- 
appear, add  more  water.  When  cool,  touch 
a  drop  of  the  liquid  to  the  tongue.  Evidently 
the  sugar  remains,  though  in  a  state  too  finely 
divided  to  be  seen.  This  is  called  a  solution, 
the  sugar  is  said  to  be  soluble  in  water,  and 
water  to  be  a  solvent  of  sugar. 


/*  —  \     X89™^ 

f  \  f  \ 

*  -  * 


Fig'  4* 


Fig.  3. 

fold  a  filter 
Figure  4,  arrange  it 
in  a  funnel  (Fig.  5),  and 
pour  the  so- 
lution upon 


it,  catching  what  passes  through,  which  is  called  the 
filtrate,  in  another  t.t.  that  rests  in  a  receiver  (Fig. 
5).  After  filtering,  notice  whether  any  residue  is  left 
on  the  filter  paper.  Taste  a  drop  of  the  filtrate. 
Has  sugar  gone  through  the  filter  ?  If  so,  what  do  you 
infer  of  substances  in  solution  passing  through  a 
filter?  Save  half  the  filtrate  for  Experiment  5,  and 
dilute  the  other  half  with  two  or  three  times  its  own 
volume  of  water.  Shake  well,  and  taste. 


Fig.  5. 


4  WHAT  CHEMISTRY  IS. 

We  might  have  diluted  the  sugar  solution  many  times 
more,  and  still  the  sweet  taste  would  have  remained.  Thus 
the  small  quantity  of  sugar  would  be  distributed  through 
the  whole  mass,  and  be  very  finely  divided. 

By  other  experiments  a  much  finer  subdivision  can  be 
made.  A  solution  of  .00000002s  of  the  red  coloring  mat- 
ter, fuchsine,  in  lcc  of  alcohol  gives  a  distinct  color. 

Such  experiments  would  seem  to  indicate  that  there  is 
no  limit  to  the  divisibility  of  matter.'  But  considerations 
which  we  cannot  discuss  here  lead  to  the  belief  that  such 
a  limit  does  exist;  that  there  are  particles  of  sugar,  and  of 
all  substances,  which  are  incapable  of  further  division  with- 
out entirely  changing  the  nature  of  the  substance.  To 
these  smallest  particles  the  name  molecules  is  given. 

A  mass  is  any  portion  of  a  substance  larger  than  a  mole- 
cule ;  it  is  an  aggregation  of  molecules. 
?  A  molecule  is  the  smallest  particle  of  a  substance  that 
can  exist  alone. 

A  substance  in  solution  may  be  in  a  more  finely  divided  state  than 
otherwise,  but  it  is  not  necessarily  in  its  ultimate  state  of  division. 

7.  A  Chemical  Change.  —  Cannot  this  smallest  par- 
ticle of  sugar,  the  molecule,  be  separated  into  still  smaller 
particles  of  something  else  ?  May  it  not  be  a  compound 
body,  and  will  not  some  force  separate  it  into  two  'or  more 
substances?  The  next  experiment  will  answer  the  ques- 
tion. 

Experiment  5.  —  Take  the  sugar  solution  saved  from  Experiment 
4,  and  add  slowly  4CC  of  strong  sulphuric  acid.  Note  any  change  of 
color,  also  the  heat  of  the  t.t.  Add  more  acid  if  needed. 

A  substance  entirely  different  in  color  and  properties 
has  been  formed.  Now  either  the  sugar,  the  acid,  or  the 


WHAT  CHEMISTRY  IS.  5 

water  has  undergone  a  chemical  change.  It  is,  in  fact,  the 
sugar.  But  the  molecule  is  the  smallest  particle  of  sugar 
possible.  The  acid  must  have  either  added  something  to 
the  sugar  molecules,  or  subtracted  something  from  them. 
It  was  the  latter.  Here,  then,  is  a  force  entirely  different 
from  the  one  which  tends  to  reduce  masses  to  molecules. 
The  molecule  has  the  same  properties  as  the  mass.  Only 
a  physical  force  was  used  in  dissolving  the  sugar,  and  no 
heat  was  liberated.  The  acid  has  changed  the  sugar  into 
a  black  mass,  in  fact  into  charcoal  or  carbon,  and  water ; 
and  heat  has  been  produced.  A  chemical  change  has  been 
brought  about. 

From  this  we  see  that  molecules  are  not  the  ultimate 
divisions  of  matter.  The  smallest  sugar  particles  are 
made  up  of  still  smaller  particles  of  other  things  which 
do  not  resemble  sugar,  as  a  word  is  composed  of  letters 
which  alone  do  not  resemble  the  word.  But  can  the  char- 
coal itself  be  resolved  into  other  substances,  and  these  into 
still  others,  and  so  on  ?  Carbon  is  one  of  the  substances 
from  which  nothing  else  has  been  obtained.  There  are 
about  seventy  others  which  have  not  been  resolved.  These 
are  called  elements,  and  out  of  them  are  built  all  the  com- 
pounds —  mineral,  vegetable,  and  animal  —  which  we 
know. 

8.  An  element  is  a  chemically  indivisible  substance, 
or  one  from  which  nothing  else  can  be  extracted. 

A  compound  is  a  substance  which  is  made  up  of  ele- 
ments united  in  exact  proportions  by  a  force  called  chem- 
isin,  or  chemical  affinity. 

A  mixture  is  composed  of  two  or  more  elements  or 
compounds  blended  together,  but  not  held  by  any  chemi- 
cal attraction. 


6  WHAT  CHEMISTRY  IS. 

To  which  of  these  three  classes  does  sugar  belong?  Carbon?  The 
solution  of  sugar  in  water  ? 

Carbon  is  an  element;  we  call  its  smallest  particle  an 
atom. 

An  atom  is  the  smallest  particle  of  an  element  that  can 
enter  into  combination.  Atoms  are  indivisible  and  usually 
do  not  exist  alone.  Both  elements  and  compounds  have 
molecules,  but  only  elements  have  atoms. 

The  molecule  of  an  element  usually  contains  two  atoms ; 
that  of  a  compound  may  have  two,  or  it  may  have  hundreds. 
For  a  given  compound  the  number  is  always  definite. 

Chemism  is  the  force  that  binds  atoms  together  to  form 
molecules.  The  sugar  molecule  contains  atoms,  forty-five 
in  all,  of  three  different  elements :  carbon,  hydrogen,  and 
oxygen.  That  of  salt  has  two  atoms :  one  of  sodium,  one 
of  chlorine.  Should  we  say  "  an  atom  of  sugar  "  ?  Why  ? 
Of  what  is  a  mass  of  sugar  made  up  ?  A  molecule  ?  A  mass 
of  carbon  ?  A  molecule  ?  Did  the  chemical  affinity  of  the 
acid  break  up  masses  or  molecules  ?  In  this  respect  it  is  a 
type  of  all  chemical  action.  The  distinction  between  phys- 
ics and  chemistry  is  here  well  shown.  The  molecule  is 
the  unit  of  the  physicist,  the  atom  that  of  the  chemist. 
However  large  the  masses  changed  by  chemical  action,  that 
action  is  always  on  the  individual  molecule,  the  atoms  of 
which  are  separated.  If  the  molecule  were  an  indivisible 
particle,  no  science  of  chemistry  would  be  possible.  The 
physicist  finds  the  properties  of  masses  of  matter  and  re- 
solves them  into  molecules,  the  chemist  breaks  up  the 
molecule  and  from  its  atoms  builds  up  other  compounds. 

Analysis  is  the  separation  of  compounds  into  their 
elements. 

Synthesis  is  the  building  up  of  compounds  from  their 
elements. 


WHAT  CHEMISTRY  IS.  7 

Of  which  is  the  sugar  experiment  an  example? 

Metathesis  is  an  exchange  of  atoms  in  two  different 
compounds ;  it  gives  rise  to  still  other  compounds. 

A  chemical  change  may  add  something  to  a  substance, 
or  subtract  something  from  it,  or  it  may  both  subtract 
and  add,  making  a  new  substance  with  entirely  different 
properties.  Sulphur  and  carbon  are  two  stable  solids. 
The  chemical  union  of  the  two  forms  a  volatile  liquid. 
A  substance  may  be  at  one  time  a  solid,  at  another  a 
liquid,  at  another  a  gas,  and  yet  not  undergo  any  chemi- 
cal change,  because  in  each  case  the  chemical  composition 
is  identical. 

State  which  of  these  are  chemical  changes :  rusting  of 
iron,  falling  of  rain,  radiation  of  heat,  souring  of  milk, 
evaporation  of  water,  decay  of  vegetation,  burning  of 
wood,  breaking  of  iron,  bleaching  of  cloth.  Give  any 
other  illustrations  that  occur  to  you. 

Chemistry  treats  of  matter  in  its  simplest  forms,  and  of 
the  various  combinations  of  those  simplest  forms. 


CHAPTER  III. 

MOLECULES  AND  ATOMS. 

9.  Molecules  are  Extremely  Small.  —  It  has  been 
estimated  that  a  liter  of  any  gas  at  0°  and  760mm  pres- 
sure contains  1024  molecules,  i.e.  one  with  twenty-four 
ciphers. 

Thomson  estimates  that  if  a  drop  of  water  were  magnified  to  the  size 
of  the  earth,  and  its  molecules  increased  in  the  same  proportion,  they 
would  be  larger  than  fine  shot,  but  not  so  large  as  cricket  balls. 

A  German  has  recently  obtained  a  deposit  of  silver  two-millionths  of  a 
millimeter  thick,  and  visible  to  the  naked  eye.  The  computed  diameter 
of  the  molecule  is  only  one  and  a  half  millionths  of  a  millimeter. 

By  a  law  of  chemistry  there  is  the  same  number  of 
molecules  in  a  given  volume  of  every  gas,  if  the  tempera- 
ture and  pressure  are  the  same.  Hence,  all  gaseous  mole- 
cules are  of  the  same  size,  including,  of  course,  the  sur- 
rounding space.  They  are  in  rapid  motion,  and  the  lighter 
the  gas  the  more  rapid  the  motion.  This  gives  rise  to 
diffusion.  See  page  114. 

1C.  We  Know  Nothing  Definite  of  the  Form  of 
Molecules.  —  In  this  book  they  will  always  be  represented 
as  of  the  same  size,  that  of  two  squares,  I  I.  A  molecule 
is  itself  composed  of  atoms,  —  from  two  to  several  hun- 
dred. The  size  of  the  atom  of  most  elements  we  represent 
by  one  square,  D. 


MOLECtTLES  AND  ATOMS.  9 

11.  Atoms.  —  If  the  gaseous  molecules  be  of  the  same 
size,  it  is  clear  that  either  the  atoms  themselves  must  be 
condensed,  or  the  spaces  between  them  must  be  smaller 
than  before.     We  suppose  the  latter  to  be  the  case,  and 
that  they  do  not  touch  one  another,  the  same  thing  being 
true    of  molecules.      Atoms   composing   sugar   must   be 
crowded  nearer  together  than  those  of  salt.     These  atoms 
are  probably  in  constant  motion  in  the  molecule,  as  the 
latter  is  in  the  mass.     If  we  regard  this  square  as 

a  mass  of  matter,  the  dots  may   represent  mole- 
cules ;  if  we  call  it  a  molecule,  the  dots  may  be 
called  atoms,  though  many  molecules  have  no  more  than 
two  or  three  atoms. 

The  following  experiments  illustrate  the  union  of  atoms 
to  form  molecules,  and  of  elements  to  form  compounds. 

12.  Union  of  Atoms. 

Experiment  6.  —  Mix,  on  a  paper,  &  of  iron  turnings,  and  the 
same  bulk  of  powdered  sulphur,  and  transfer  them  to  an  ignition 
tube,  a  tube  of  hard  glass  for  withstanding  high  temperatures.  Hold 
the  tube  in  the  flame  of  a  burner  till  the  contents  have  become  red-hot. 
After  a  minute  break  it  by  holding  it  under  a  jet  of  water.  Put  the 
contents  into  an  evaporating-dish,  and  look  for  any  uncombined  iron 
or  sulphur.  Both  iron  and  sulphur  are  elements.  Is  this  an  example 
of  synthesis  or  of  analysis?  Why?  Is  the  chemical  union  between 
masses  of  iron  and  sulphur,  or  between  molecules,  or  between  atoms  ? 
Is  the  product  a  compound,  an  element,  or  a  mixture  ? 

Experiment  7.  —  Try  the  same  experiment,  using  copper  instead 
of  iron.  The  full  explanation  of  these  experiments  is  given  on 
page  13. 


CHAPTER  IV. 

ELEMENTS  AND  BINARIES. 

13.  About    Seventy   Different    Elements    are   now 
Recognized,  half  of  which  have  been  discovered  within 
little  more  than  a  century.    These  differ  from  one  another 
in  (1)  atomic  weight,  (2)  physical  and  chemical  proper- 
ties, (3)  mode  of  occurrence,  etc.     Page  12  contains  the 
most  important  elements. 

The  symbol  of  an  element  is  usually  the  initial  letter  or 
letters  of  its  Latin  name,  and  stands  for  one  atom  of  the 
element.  C  is  the  symbol  for  carbon,  and  represents  one 
atom  of  it.  O  means  one  atom  of  oxygen.1  Write,  ex- 
plain, and  memorize  the  symbols  of  the  elements  in  heavy 
type,  page  12. 

14.  The  Atomic  Weight  of  an  element  is  the  weight  of 
its  atom  compared  with  that  of  hydrogen.     H  is  taken  as 
the  standard  because  it  has  the  least  atomic  weight.     The 
atomic  weight  of   O  is   16,  which   means   that   its  atom 
weighs  16  times  as  much  as  the  H  atom.     Every  symbol, 
then,  stands  for  a  definite  weight  of  the  element,  i.e.  its 
atomic  weight,  as  well  as  for  its  atom. 

How  much  bromine  by  weight  does  Br  stand  for? 
What  do  these  symbols  mean  —  As,  Na,  N,  P?  If  O 
represents  one  atom,  how  much  does  O2  or  2  O  stand 
for?  How  much  by  weight?  Most  elements  have  two 

1  *  The  symbols  of  elements  will  also  be  used  in  this  book  to  stand  for  an  indefinite 
quantity  of  them ;  e.g.  O  will  be  used  for  oxygen  in  general  as  well  as  for  one  atom.  The 
text  will  readily  decide  when  symbols  have  a  definite  meaning,  and  when  they  are  used 
in  place  of  words. 


ELEMENTS   AND   BINARIES.  11 

atoms  in  the   molecule.      How  many  molecules  in  6  H? 
ION?  S8?  V 

The  symbol  of  a  compound  is  formed  by  writing  in  suc- 
cession the  symbols  of  the  elements  of  which  it  is  com- 
posed. How  many  atoms  in  the  following  molecules,  and 
how  many  of  each  element:  C2H6O?  HNO3?  PbSO4? 
MgCl2?  Hg2(N03)2? 

15.  The  Simplest  Compounds  are  Binaries.  —  A  bi- 
nary is  a  substance  composed  of  two  elements ;  e.g.  com- 
mon salt,  which  is  a  compound  of  sodium  and  chlorine. 
Its  symbol  is  NaCl,  its  chemical  name  sodium  chloride. 
The  ending  ide  is  applied  to  the  last  name  of  binaries. 
How  many  parts  by  weight  of  Na  and  of  Cl  in  NaCl? 
What  is  the  molecular  weight,  i.e.  the  weight  of  its  mole- 
cule? Name  KC1.  How  many  atoms  in  its  molecule?  Parts 
by  weight  of  each  element?  Molecular  weight?  Does  the 
symbol  stand  for  more  than  one  molecule?  How  many 
molecules  in  4 NaCl?  How  many  atoms  of  Na  and  of  Cl? 
Name  these:  HC1,  NaBr,  Nal,  KBr,  AgCl,  Agl,  HBr, 
HI,  HF,  HgO,  ZnO,  ZnS,  MgO,  CaO.  Compute  the  pro- 
portion by  weight  of  each  element  in  the  last  three. 

A  coefficient  before  the  symbol  of  a  compound  includes 
all  the  elements  of  the  symbol,  and  shows  the  number 
of  molecules.  How  many  in  these :  6  KBr  ?  3  SnO  ? 
12  NaCl  ?  How  many  atoms  of  each  element  in  the  above  ? 

An  exponent,  always  written  below,  applies  only  to  the 
element  after  which  it  is  written,  and  shows  the  number 
of  atoms.  Explain  these :  AuCl3,  ZnCl2,  Hg2Cl2. 

Write  symbols  for  four  molecules  of  sodium  bromide,  one  of  silver 
iodide  (always  omit  coefficient  one),  eight  of  potassium  bromide,  ten 
of  hydrogen  chloride ;  also  for  one  molecule  pf  each  of  tbege :  hydrogen 
fluoride,  potassium  iodide,  silver  chloride, 


12 


ELEMENTS    AND   BINARIES. 


In  all  the  above  cases  the  elements  have  united  atom  for  atom. 
Some  elements  will  not  so  unite.  In  CaCl.2  how  many  atoms  of  each 
element  ?  Parts  by  weight  of  each  ?  Give  molecular  weight.  Is  the 
size  of  the  molecule  thereby  changed?  See  page  8.  Name  these,  give 
the  number  of  atoms  of  each  element  in  the  molecule,  and  the  propor- 
tion by  weight,  also  their  molecular  weights :  AuCl3,  ZnCl2,  MnCl2, 
Na.,0,  K2S,  H3P,  H4C. 

Principal  Elements. 


Name. 

Sym. 

At.  Wt. 

Valence. 

Vap.D. 

At.  Vol. 

Mol.  Vol. 

State. 

Aluminium 

Al 

27. 

II,  IV 

Solid 

Antimony 

Sb 

120. 

III,  V 

.  . 

n 

Arsenic 

As 

75. 

III,  V 

150. 

D 

CD 

« 

Barium 

Ba 

137. 

II 

" 

Bismuth 

Bi 

210. 

III,  V 

« 

Boron 

B 

11. 

III 

« 

Bromine 

Cadmium 

Br 
Cd 

80. 
112. 

I,  (V) 

II 

80. 
56. 

i 

0 

Liquid 
Solid 

Calcium 

Ca 

40. 

II 

.  .  . 

« 

Carbon 

C 

12. 

(II),  IV 

" 

Chlorine 

Cl 

35.5 

I.  (V) 

35.5 

n" 

rn 

Gas 

Chromium 

Cr 

52. 

(II),  IV,  VI 

. 

Solid 

Cobalt 

Co 

59. 

II,  IV 

.  .  . 

" 

Copper 

Cu 

63. 

I,  II 

" 

Fluorine 

Gold 

F 
Au 

19. 
196. 

I,  00 

(I),  III 

Gas 

Solid 

Hydrogen 

H 

1. 

1. 

n" 

£3 

Gas 

Iodine 

I 

127. 

1,00 

127. 

Solid 

Iron 

Fe 

56. 

11,  IV,  (VI) 

.  .  . 

" 

Lead 

Pb 

206. 

II,  IV 

« 

Lithium 

Li 

7. 

I 

. 

.  .  . 

.  .  . 

« 

Magnesium 

Mg 

24. 

II 

" 

Manganese 

Mn 

55. 

II,  IV,  VI 

.  .  . 

" 

Mercury 

Hg 

200. 

I,  II 

100. 

ED 

E±] 

Liquid 

Nickel 

Ni 

59. 

II,  IV 

Solid 

Nitrogen 
Oxygen 

N 
0 

14. 
16. 

(I),  III,  V 

14. 
16. 

0" 

= 

Gas 

(4 

Phosphorus 

P 

31. 

(I),  III,  V 

62. 

D 

Solid 

Platinum 

Pt 

197. 

(II),  IV 

.  .  . 

<« 

Potassium 

K 

39. 

I 

.  .  . 

.  .  . 

" 

Silicon 

Si 

28. 

IV 

.  .  . 

« 

Silver 

Ag 

108. 

I 

« 

Sodium 

Na 

23. 

I 

.  .  . 

.  .  . 

« 

Strontium 

Sr 

87. 

II 

. 

« 

Sulphur 

S 

32. 

II,  IV,  (VI) 

32(96) 

D" 

CD 

« 

Tin 

Sn 

118. 

II,  IV 

.  .  . 

.  .  . 

" 

Zinc 

Zn 

65. 

II 

32.5 

CD 

CD 

« 

ELEMENTS   AND   BINARIES.  13 

If  more  than  one  atom  of  an  element  enters  into  the  composition  of 
a  binary,  a  prefix  is  often  used  to  denote  the  number.  SO2  is  called 
sulphur  dioxide,  to  distinguish  it  from  SO3,  sulphur  trioxide.  Name 
these :  CO2,  SiO2,  MnO2.  The  prefixes  are :  mono  or  proto,  one ;  di  or 
bi,  two ;  tri  or  ter,  three ;  tetra,  four ;  pente,  five ;  hex,  six ;  etc.  Diar- 
senic  pentoxide  is  written,  As2O5.  Symbolize  these :  carbon  protoxide, 
diphosphorus  pentoxide,  diphosphorus  trioxide,  iron  disulphide,  iron 
protosulphide.  Often  only  the  prefix  of  the  last  name  is  used. 

16.  An  Oxide  is  a  Compound  of  Oxygen  and  Some 
Other  Element,  as  HgO.  What  is  a  chloride  ?  Define  sul- 
phide, phosphide,  arsenide,  carbide,  bromide,  iodide,  fluor- 
ide. 

In  Experiment  6,  where  S  and  Fe  united,  the  symbol  of 
the  product  was  FeS.  Name  it.  How  many  parts  by 
weight  of  each  element  ?  What  is  its  molecular  weight  ? 
To  produce  FeS  a  chemical  union  took  place  between 
each  atom  of  the  Fe  and  of  the  S.  We  may  express  this 
reaction,  i.e.  chemical  action,  by  an  equation:  — 

Iroa+  Sulphur  =  J^ 

Or,  using  symbols,  Fe  +      S       -=•    FeS. 

Using  atomic  weights,      66+32      =     88. 

These  equations  are  explained  by  saying  that  56  parts 
by  weight  of  iron  unite  chemically  with  32  parts  by  weight 
of  sulphur  to  produce  88  parts  by  weight  of  iron  sulphide. 
This,  then,  indicates  the  proportion  of  each  element  which 
combines,  and  which  should  be  taken  for  the  experiment. 
If  56*  of  Fe  be  used,  32«  of  S  should  be  taken.  If  we  use 
more  than  56  parts  of  Fe  with  32  of  S,  will  it  all  combine  ? 
If  more  than  32  of  S  with  56  of  Fe  ?  There  is  found  to  be 
a  definite  quantity  of  each  element  in  every  chemical  com- 
pound. Symbols  would  have  no  meaning  ii  this  were  not  so. 

Write  and  explain  the  equation  for  the  experiment  with  copper  and 
sulphur,  using  names,  symbols,  and  weights,  as  above. 


CHAPTER  V. 

MANIPULATION. 

17.  To  Break  Glass  Tubing. 

Experiment  8.  —  Lay  the  tubing  on  a  flat  surface,  and  draw  a 
sharp  three-cornered  file  two  or  three  times  at  right  angles  across  it 
where  it  is  to  be  broken,  till  a  scratch  is  made.  Take  the  tube  in  the 
hands,  having  the^  two  thumbs  nearly  opposite  the  scratch,  and  the 
fingers  on  the  other  side.  Press  outward  quickly  with  the  thumbs, 
and  at  the  same  time  pull  the  hands  strongly  apart,  and  the  tubing 
should  break  squarely  at  the  scratch. 

To  break  large  tubing,  or  cut  off  bottles,  lamp  chimneys,  etc.,  first 
make  a  scratch  as  before ;  then  heat  the  handle  of  a  file,  or  a  blunt 
iron  —  in  a  blast-lamp  flame  by  preference  —  till  it  is  red-hot,  and  at 
once  press  it  against  the  scratch  till  the  glass  begins  to  crack.  The 
fracture  can  be  led  in  any  direction  by  keeping  the  iron  just  in  front 
of  it.  Re-heat  the  iron  as  often  as  necessary. 

18.  To  Make  Ignition-Tubes. 

Experiment  9.  — Hold  the  glass  tubing  between  the  thumb  and 
forefinger  of  each  hand,  resting  it  against  the  second  finger.  Heat  it 
in  the  upper  flame,  slowly  at  first,  then  strongly,  but  heat  only  a  very 
small  portion  in  length,  and  keep  it  in  constant  rotation  with  the  right 
hand.  Hold  it  steadily,  and  avoid  twisting  it  as  the  glass  softens. 
The  yielding  is  detected  by  the  yellow  flame  above  the  glass  and  by 
an  uneven  pressure  on  the  hands.  Pull  it  a  little  as  it  yields,  then  heat 
a  part  just  at  one  side  of  the  most  softened  portion.  Rotate  constantly 
without  twisting,  and  soon  it  can  be  separated  into  two  closed  tubes. 
No  thread  should  be  attached ;  but  if  there  be  one,  it  can  be  broken 
off  and  the  end  welded.  The  bottom  can  be  made  more  symmetrical 
by  beating;  it  red-hot,  then  blowing,  gradually,  into  the  open  end,  this, 


MANIPULATION.  15 

being  inserted  in  the  mouth.  The  parts  should  be  annealed  by  hold- 
ing above  the  flame  for  a  short  time,  to  cool  slowly. 

For  hard  glass  —  Bohemian — or  large  tubes,  the  blast-lamp  or  blow- 
pipe is  needed.  In  the  blast-lamp  air  is  forced  out  with  illuminating 
gas.  This  gives  a  high  degree  of  heat.  Bulbs  can  be  made  in  the 
same  way  as  ignition-tubes,  and  thistle-tubes  are  made  by  blowing 
out  the  end  of  a  heated  bulb,  and  rounding  it  with  charcoal. 

19.  To  Bend  Glass  Tubing. 

Experiment  10.  —  Hold  the  tube  in  the  upper  flame.  Rotate  it  so 
as  to  heat  all  parts  equally,  and  let  the  flame  spread  over  3  or  4cm  in 
length.  When  the  glass  begins  to  yield, 
without  removing  from  the  flame  slowly 
bend  it  as  desired.  Avoid  twisting,  and  be 
sure  to  have  all  parts  in  the  same  plane; 
also  avoid  bending  too  quickly,  if  you  would 
have  a  well-rounded  joint.  Anneal  each  bend 
as  made.  Heated  glass  of  any  kind  should 
never  be  brought  in  contact  with  a  cool 
body.  For  making  O,  H,  etc.,  a  glass  tube 

—  delivery-tube  —  50cm  long  should  have  three  bends,  as  in  Figure  6. 
The  pupil  should  first  experiment  with  short  pieces  of  glass,  10  or 
15cm  long.  An  ordinary  gas  flame  is  the  best  for  bending  glass. 

20.  To  Cut  Glass. 

Experiment  11.  —  Lay  the  glass  plate  on  a  flat  surface,  and  draw 
a  steel  glass-cutter  —  revolving  wheel  —  over  it,  holding  this  against  a 
ruler  for  a  guide,  and  pressing  down  hard  enough  to  scratch  the  glass. 
Then  break  it  by  holding  between  the  thumb  and  fingers,  having  the 
thumbs  on  the  side  opposite  to  the  scratch,  and  pressing  them  out- 
ward while  bending  the  ends  of  the  glass  inward.  The  break  will 
follow  the  scratch. 

Holes  can  be  bored  through  glass  and  bottles  with  a  broken  end  of 
a  round  file  kept  wet  with  a  solution  of  camphor  in  oil  of  turpentine. 

21.  To  Perforate  Corks. 

Experiment  12.  —  First  make  a  small  hole  in  the  cork  with  the 
pointed  handle  of  a  round  —  rat-tail  —  file.  Have  the  hole  perpendic- 


16  MANIPULATION. 

ular  to  the  surface  of  the  cork.  This  can  be  done  by  holding  the  cork 
in  the  left  hand  and  pressing  against  the  larger  surface,  or  upper  part, 
of  the  cork,  with  the  file  in  the  right  hand.  Only  a  mere  opening  is 
made  in  this  way,  which  must  be  enlarged  by  the  other  end  of  the  file. 
A  second  or  third  file  of  larger  size  may  be  employed,  according  to 
the  size  of  the  hole  to  be  made,  which  must  be  a  little  smaller  than 
the  tube  it  is  to  receive,  and  perfectly  round. 


CHAPTER   VI. 

OXYGEN. 

22.    To  Obtain   Oxygen. 

Experiment  13.  —  Take  5&  of  crystals  of  potassium  chlorate 
(KClOg)  and,  without  pulverizing,  mix  with  the  same  weight  of  pure 
powdered  manganese  dioxide  (MnO2).  Put  the  mixture  into  a  t.t.,  and 
insert  a  d.t.  —  delivery-tube  —  having  the  cork  fit  tightly.  Hang  it  on 
a  r.s.  —  ring-stand,  —  as  in  Figure  7,  having  the  other  end  of  the  d.t. 


Fig.  7. 

under  the  shelf,  in  a  pneumatic  trough,  filled  with  water  just  above 
the  shelf.  Fill  three  or  more  receivers  —  wide-mouthed  bottles  —  with 
water,  cover  the  mouthx>f  each  with  a  glass  plate,  invert  it  with  its 
mouth  under  water,  and  put  it  on  the  shelf  of  the  trough,  removing 
the  plate.  No  air  should  be  in  the  bottles.  Have  the  end  of  the  d.t. 
so  that  the  gas  will  rise  through  the  orifice.  Hold  a  lighted  lamp  in 
the  hand,  and  bring  the  flame  against  the  mixture  in  the  t.t.  Keep 


18  OXYGEN. 

the  lamp  slightly  in  motion,  with  the  hand,  so  as  not  to  break  the  t.t. 

by  over-heating  in  one  place.     Heat  the  mixture  strongly,  if  necessary. 

The  upper  part  of  the  t.t.  it  filled  with  air :  allow  this  to  escape  for  a 

few  seconds ;  then  move  a  receiver  over  the  orifice,  and  fill  it  with  gas. 

As  soon  as  the  lamp  is  taken  away,  remove  the  d.t.  from  the  water. 

The  gas  contracts,  on  cooling,  and  if  not  removed,  water  will  be  drawn 

over,  and  the  t.t.  will  be  broken.  Let  the  t.t.  hang  on  the  r.s.  till  cool. 
With  glass  plates  take  out  the  receivers,  leaving 
them  covered,  mouth  upward  (Fig.  8),  with  little  or 
no  water  inside.  When  cool,  the  t.t.  may  be  cleaned 
with  water,  by  covering  its  mouth  with  the  thumb  or 
hand,  and  shaking  it  vigorously. 

What  elements,  and  how  many,  in  KC1O3? 
Fig.  s.  jn  MnO2?  It  is  evident  that  each  of  these 
compounds  contains  O.  Why,  then,  could  we  not  have 
taken  either  separately,  instead  of  mixing  the  two  ?  This 
could  have  been  done  at  a  sufficiently  high  temperature. 
MnO2  requires  a  much  higher  temperature  for  dissociation, 
i.e.  separation  into  its  elements,  than  KC1O3,  while  a  mix- 
ture of  the  two  causes  O  to  come  off  from  KC1O3  at  a 
lower  temperature  than  if  alone.  It  is  not  known  that 
MnO2  suffers  any  change. 

Each  molecule  of  potassium  chlorate  undergoes  the  fol- 
lowing change :  — 

Potassium      Potassium  ,  ,-> 
Chlorate  =   Chloride  +  OxySen' 

KC103  =     KC1     +30. 

Is  this  analysis  or  synthesis  ?  Complete  the  equation,  by 
using  weights,  and  explain  it.  Notice  whether  the  right- 
hand  member  of  the  equation  has  the  same  number  of 
atoms  as  the  left.  Has  anything  been  lost  or  gained? 
What  element  has  heat  separated?  Does  the  experiment 
show  whether  O  is  very  soluble  in  water?  How  many 
grams  of  O  are  obtainable  from  122.5g  KC1O3  ? 


OXYGEN.  19 


PROPERTIES. 

23.  Combustion  of  Carbon. 

Experiment  14.  —  Examine  the  gas  in  one  of  the  receivers. 
Put  a  lighted  splinter  into  the  receiver,  sliding  along  the  glass  cover. 
Remove  it,  blow  it  out,  and  pirt  in  again  while  glowing.  Is  it  re- 
kindled ?  Repeat  till  it  will  no  longer  burn.  Is  the  gas  a  supporter 
of  combustion?  How  did  the  combustion  compare  with  that  in  air? 
Is  it  probable  that  air  is  pure  O  ?  Why  did  the  flame  at  last  go  out  ? 
Has  the  O  been  destroyed,  or  chemically  united  with  something  else? 

Wood  is  in  part  C.  CO2  is  formed  by  the  combustion  ; 
name  it.  The  equation  is  C  +  2  O  —  CO2.  Affix  the  names 
and  weights.  Is  CO2  a  supporter  of  combustion  ?  Note 
that  when  C  is  burned  with  plenty  of  O,  CO2  is  always 
formed,  and  that  no  matter  how  great  the  conflagration, 
the  union  is  atom  by  atom.  Combustion,  as  here  shown,  is 
only  a  rapid  union  of  O  with  some  other  substance,  as  C 
or  H. 

24.  Combustion  of  Sulphur. 

Experiment  15.  —  Hollow  out  one  end  of  a  piece  of  electric-light 
pencil,  or  of  crayon,  3cm  long,  and  attach  it  to  a  Cu  wire  (Fig.  9). 
Put  into  this  a  piece  of  S  as  large  as  a  pea,  ignite  it 
by  holding  in  the  flame,  and  then  hold  it  in  a  re- 
ceiver of  O.  Note  the  color  and  brightness  of  the 
flame,  and  compare  with  the  same  in  the  air.  Also 
note  the  color  and  odor  of  the  product.  The  new  gas 
is  SO2.  Name  it,  and  write  the  equation  for  its  pro- 
duction from  S  and  O.  How  do  you  almost  daily 
perform  a  similar  experiment?  Is  the  product  a 
supporter  of  combustion  ? 

25.  Combustion  of  Phosphorus.  Fig.  9. 

Experiment  16.  —  With  forceps,  which  should  always  be  used  in 
handling  this  element,  put  a  bit  of  P,  half  as  large  as  the  S  above, 


ir  1  7  BE  SI  T 


20  OXYGEN. 

into  the  crayon,  called  a  deflagrating-spoon.  Heat  another  wire,  toi 
it  to  the  P,  and  at  once  lower  the  latter  into  a  receiver  of  O.  Notice  We 
combustion,  the  color  of  the  flame  and  of  the  product.  After  removing, 
be  sure  to  burn  every  bit  of  P  by  holding  it  in  a  flame,  as  it  is  liable 
to  take  fire  if  left.  The  product  of  the  combustion  is  a  union  of  what 
two  elements  ?  Is  it  an  oxide  ?  Its  symbol  is  P2O5.  Write  the  equa- 
tion, using  symbols;  names,  and  weights.  Towards  the  close  of  the 
experiment,  when  the  O  is  nearly  all  combined,  P2O3  is  formed,  as  it 
is  also  when  P  oxidizes  at  a  low  temperature.  Name  it  and  write  the 
equation. 

26.  Combustion  of  Iron. 

Experiment  17.  —  Take  in  the  forceps  a  piece  of  iron  picture-cord 
wire  6  or  8cm  long,  hold  one  end  in  the  flame  for  an  instant,  then  dip 
it  into  some  S.  Enough  S  will  adhere  to  be  set  on  fire  by  holding  it 
in  the  flame  again.  Then  at  once  dip  it  into  a  receiver  of  O  with  a 
little  water  in  the  bottom.  The  iron  will  burn  with  scintillations.  Is 
this  analysis  or  synthesis  ?  What  elements  combine  ?  A  watch-spring, 
heated  to  take  out  the  temper,  may  be  used,  but  picture-wire  is  better. 

The  product  is  Fe3O4.  Write  the  equation.  How  much  Fe  by 
weight  in  the  formula?  How  much  O?  What  per  cent  by  weight  of 
Fe  in  the  compound?  Multiply  the  fractional  part  by  100.  What 
per  cent  of  O  ?  What  per  cent  of  CO2  is  C  ?  O2  ?  Find  the  percent- 
age composition  of  SO2.  P2O5. 

From  the  last  five  experiments  what  do  you  infer  of  the  tendency 
of  O  to  unite  with  other  elements  ? 

27.  Oxygen  is  a  Gas  without  Color,  Odor,  or  Taste. 

—  It  is  chemically  a  very  active  element ;  that  is,  it  unites 
with  almost  everything.  Fluorine  is  the  only  element  with 
which  it  will  not  combine.  When  oxygen  combines  with 
a  single  element,  what  is  the  compound  called?  We  have 
found  that  O  makes  up  a  certain  portion  of  the  air ;  later, 
we  shall  see  how  large  the  proportion  is.  Its  tendency  to 
combine  with  almost  everything  is  a  reason  for  the  decay, 
rust,  and  oxidation  of  so  many  substances,  and  for  confla- 
grations, great  and  small.  New  compounds  are  thus 


OXYGEN.  21 

formed,  of  which  O  constitutes  one  factor.  Water,  H2O, 
is  only  a  chemical  union  of  O  and  H.  Iron  rust,  Fe2O3  and 
H2O,  is  composed  of  O,  Fe,  and  water.  The  burning  of 
wood  or  of  coal  gives  rise  to  carbon  dioxide,  CO2,  and 
water.  Decay  of  animal  and  vegetable  matter  is  hastened 
by  this  all-pervading  element.  O  forms  a  portion  of  all 
animal  and  vegetable  matter,  of  almost  all  rocks  and  min- 
erals, and  of  water.  It  is  the  most  abundant  of  all  ele- 
ments, and  makes  up  from  one-half  to  two-thirds  of  the 
earth's  surface.  Compute  the  proportion  of  it,  by  weight, 
in  water,  H2O.  It  is  the  union  of  O  in  the  air  with  C 
and  H  in  our  blood  that  keeps  up  the  heat  of  the  body 
arid  supports  life.  See  page  81. 

There  are  many  ways  of  preparing  this  element  besides 
the  one  given  above.  It  may  be  obtained  from  water  (Ex- 
periment 38)  and  from  many  other  compounds,  e.g.  by 
heating  mercury  oxide,  HgO. 


CHAPTER   VII. 


NITROGEN. 

28.  Separation. 

Experiment  18.  —  Fasten  a  piece  of  electric-light  pencil,  or  of 
crayon,  to  a  wire,  as  in  Experiment  15,  and  bend  the  wire  so  it  will 
reach  half-way  to  the  bottom  of  a  receiver.  Using  forceps,  put 
into  the  crayon  a  small  piece  of  phosphorus.  Pass  the  wire  up 
through  the  orifice  in  the  shelf  of  a  p.t.  (pneumatic  trough),  hav- 
ing water  at  least  lcm  above  the  shelf.  Heat  another  wire,  touch  it  to 

the  P,  and  quickly  invert  an  empty  re- 
ceiver over  the  P,  having  the  mouth 
under  water,  so  as  to  admit  no  air  (Fig. 
10).  Let  the  P  burn  as  long  as  it  will, 
then  remove  the  wire  and  the  crayon,  let- 
ting in  no  air.  Note  the  color  of  the  pro- 
duct, and  leave  till  it  is  tolerably  clear, 
then  remove  the  receiver  with  a  glass 
plate,  leaving  the  water  in  the  bottom. 
Do  the  fumes  resemble  those  of  Ex- 
periment 16  ?  Does  it  seem  likely 
that  part  of  the  air  is  O?  Why  a 
part  only?  Find  what  proportion  of  the  receiver  is  filled  with  water 
by  measuring  the  water  with  a  graduate ;  then  fill  it  with  water  and 
measure  that;  compute  the  percentage  which  the  former  is  of  the 
latter.  What  proportion  of  the  air,  then,  is  O  ?  What  was  the  only 
means  of  escape  for  the  P2O5  and  P2O3  formed  ?  These  products  are 
solids.  Are  they  soluble  in  water?  Compute  the  percentage  com- 
position, always  by  weight,  of  P2O3  and  P2O5. 

The  gas  left  in  the  receiver  is  evidently  not  O.  Experiment  19  will 
prove  this  conclusively,  and  show  the  properties  of  the  new  gas. 

29.  Properties. 

Experiment  19.  —  When  the  white  cloud  has  disappeared,  slide 
the  plate  along,  and  insert  a  burning  stick ;  try  one  that  still  glows. 


Fig.  10. 


NITROGEN.  23 

See  whether  the  P  and  S  on  the  end  of  a  match  will  burn.  Is  the 
gas  a  supporter  of  combustion  ?  Since  it  does  not  unite  with  C,  S,  or 
P,  is  it  an  active  or  a  passive  element  ?  Compare  it  with  O.  Air  is 
about  14 J  timeo  as  heavy  as  H.  Which  is  heavier,  air  or  N?  See 
page  12.  Air  or  O  ? 

Write  out  the  chief  properties,  physical  and  chemical,  of  N,  as 
found  in  this  experiment. 

3O.  Inactivity  of  N.  —  N  will  scarcely  unite  chemically 
except  on  being  set  free  from  compounds.  It  has,  how- 
ever, an  intense  affinity  for  boron,  and  will  even  go  through 
a  carbon  crucible  to  unite  with  it.  It  is  not  combined 
with  O  in  the  air ;  but  the  two  form  a  mixture  (page*  86), 
of  which  N  makes  up  four-fifths,  its  use  being  to  dilute 
the  O.  What  would  be  the  effect,  in  case  of  a  fire,  if 
air  were  pure  O  ?  What  effect  on  the  human  system? 

Growing  plants  need  a  great  deal  of  N,  but  they  are 
incapable  of  making  use  of  that  in  the  air,  on  account  of  the 
chemical  inactivity  of  the  element.  Their  supply  comes 
from  compounds  in  earth,  water,  and  air.  By  reason  of  its 
inertness  N  is  very  easily  set  free  from  its  compounds. 
For  this  reason  it  is  a  constituent  of  most  explosives,  as 
gunpowder,  nitro-glycerine,  dynamite,  etc.  These  solids, 
by  heat  or  concussion,  are  suddenly  changed  to  gases, 
which  thereby  occupy  much  more  space,  causing  an  ex- 
plosion. 

Nitrogen  exists  in  many  compounds,  such  as  the  ni- 
trates; but  the  great  source  of  it  all  is  the  atmosphere. 
See  page  85. 


CHAPTER   VIII. 

HYDROGEN. 

31.  Preparation. 

Experiment  20.  —  Prepare  apparatus  as  for  making  O.  Be  sure 
that  the  cork  perfectly  fits  both  d.t.  and  t.t.,  or  the  H  will  escape. 
Cover  5s  granulated  Zn,  in  the  t.t.,  with  10CC  H2O, 
and  add  5CC  chlorhydric  acid,  IIC1.  Adjust  as  for 
O  (Fig.  7),  except  that  no  heat  is  to  be  applied.  If 
the  action  is  not  brisk  enough,  add  more  HC1.  Col- 
lect several  receivers  of  the  gas  over  water,  adding 
small  quantities  of  HC1  when  necessary.  Observe 
the  black  floating  residuum  ;  it  is  carbon,  lead,  etc. 
With  a  glass  plate  remove  the  receivers,  keeping 
Fig.  11.  them  inverted  (Fig.  11),  or  the  H  will  escape. 

32.  The  Chemical  Change  is  as  follows:  — 


Zn  +  2  HC1   =  ZnCL,  +    2  H. 

Complete  by  adding  the  weights,  and  explain.  Notice 
that  the  water  does  not  take  part  in  tKe  change  ;  it  is 
added  to  dissolve  the  ZnCl2  formed,  and  thus  keep  it 
from  coating  the  Zn  and  preventing  further  action  of  the 
acid.  Note  also  that  Zn  has  simply  changed  places  with 
H,  one  atom  of  the  former  having  driven  off  two  atoms 
of  the  latter.  The  H,  having  nothing  to  unite  with,  is 
set  free  as  a  gas,  and  collected  over  water.  Of  course  Zn 
must  have  a  stronger  chemical  affinity  for  Cl  than  H  has, 
or  the  change  could  not  have  taken  place.  Why  one  Zn 
atom  replaces  two  H  atoms  will  be  explained  later,  as 


HYDROGEN.  25 

far  as  an  explanation  is  possible.  This  equation  should  be 
studied  carefully,  as  a  type  of  all  equations.  The  left-hand 
member  shows  what  were  taken,  i.e.  the  factors ;  the  right- 
hand  shows  what  were  obtained,  i.e.  the  products.  H2SO4 
might  have  been  used  instead  of  HC1.  In  that  case  the 
reaction,  or  equation,  would  have  been :  — 


Zn  +  H2SO4  =  ZnSO4  +    2  H. 

Iron  might  have  been  used  instead  of  zinc,  in  which  case 
the  reactions  would  have  been :  — 


cblESde 


Fe+    2HC1   =  FeCl2  +     2  H. 


Fe  +    HS0    =  FeS0    +     2H. 


Write  the  weights  and  explain  the  equations.     The  latter 
should  be  memorized. 


33.    Properties. 

Experiment  21.  —  Lift  with  the  left  hand  a  receiver 
of  H,  still  inverted,  and  insert  a  burning  splinter  with 
the  right  (Fig.  12).  Does  the  splinter  continue  to  burn? 
Does  the  gas  burn  ?  If  so,  where  ?  Is  the  light  brilliant  ? 
^jte  the  color  of  the  flame.  Is  there  any  explosion? 
Tiy  this  experiment  with  several  receivers.  Is  the  gas  a 
supporter  of  combustion?  i.e.  will  carbon  burn  in  it? 
Is  it  combustible?  i.e.  does  it  burn?  If  so,  it  unites 
with  some  part  of  the  air.  With  what  part  ? 


Fig 


26 


HYDROGEN. 


34.    Collecting  H  by  Upward  Displacement. 

Experiment  22.  —  Pass  a  d.t.  from  a  H  generator  to  the  top  of  a 
receiver  or  t.t.  (Fig.  13).  The  escaping  H  being  so  much  lighter  than 
air  will  force  the  latter  down.  To  obtain 
the  gas  unmixed  with  air,  the  d.t.  should 
tightly  fit  a  cardboard  placed  under  the 
mouth  of  the  receiver.  When  filled, 
the  receiver  can  be  removed,  inverted  as 
usual,  and  the  gas  tested.  In  this  and 
other  experiments  for  generating  IT,  a 
thistle-tube,  the  end  of  which  dips  under 
the  liquid,  can  be  used  for  pouring  in  acid, 
as  in  Figure  13. 


35.    Philosopher's    Lamp 
Musical  Flame. 


and 


Experiment  23.  —  Fit  to  a  cork  a  piece 
of  glass  tubing  10  or  15cm  long,  having 

the  outer  end  drawn  out  to  a  point  with  a  small  opening,  and  insert 
it  in  the  H  generator.  Before  igniting  the  gas  at  the  end  of  the  tube 
take  the  precaution  to  collect  a  t.t.  of  it  by  upward  dis- 
placement, and  bring  this  in  contact  with  a  flame.  If  a 
sharp  explosion  ensues,  air  is  not  wholly  expelled  from 
the  generator,  and  it  would  be  dangerous  to  light  the  gas. 
When  no  sound,  or  very  little,  follows,  light  the  escaping 
gas.  The  generation  of  H  must  not  be  too  rapid,  neither 
should  the  t.t.  be  held  under  the  face,  as  the  cork  is  liable 
to  be  forced  out  by  the  pressure  of  H.  A  safety -tube, 
similar  to  the  thistle-tube  above,  will  prevent  this.  This 
apparatus  is  called  the  "philosopher's  lamp."  Thrust  the; 
flame  into  a  long  glass  tube  1£  to  3cm  in  diameter,  as 
shown  in  Figure  14,  and  listen  for  a  musical  note. 

36.    Product  of  Burning  H  in  Air. 

Experiment  24.  —  Fill  a  tube  2  or  3cm  in  diameter      Fi»-  14- 
with  calcium  chloride,  CaCl2,  and  connect  one  end  with  a  generator 
of  H  (Fig.  15).     At  the  other  end  have  a  philosopher's  lamp-tube. 


HYDROGEN.  27 

Observing  the  usual  precautions,  light  the  gas  and  hold  over  it  a 
receiver,  till  quite  a  quantity  of  moisture  collects.  All  water  was 
taken  from  the  gas  by  the  dryer,  CaCl2.  What  is,  therefore,  the  prod- 
uct of  burning  H  in  air?  Complete  this  equation  and  explain  it: 
2H  +  O  =  ?  Figure  16  shows  a  drying  apparatus  arranged  to  hold 
CaCl2. 


Fig.  15. 

37.  Explosi ven ess  of  H. 

Experiment  25.  —  Fill  a  soda-water  bottle  of  thick  glass  with 
water,  invert  it  in  a  pneumatic  trough,  and  collect  not  over  |  full  of  H. 
Now  remove  the  bottle,  still  inverted,  letting  air  in  to  fill  the  other  f . 
Mix  the  air  and  H  by  covering  the  mouth  of  the  bottle  with  the  hand, 
and  shaking  well ;  then  hold  the  mouth  of  the  bottle,  slightly  inclined, 
in  a  flame.  Explain  the  explosion  which  follows.  If  f  was  air,  what 
part  was  O?  What  use  did  the  N"  serve?  Note  any  danger  in  ex- 
ploding H  mixed  with  pure  O.  What  proportions  of  O  and  H  by 
volume  would  be  most  dangerously  explosive?  See  page  46.  What 
proportion  by  weight? 

By  the  rapid  union  of  the  two  elements,  the  high  tem- 
perature suddenly  expanded  the  gaseous  product,  which 
immediately  contracted ;  both  expansion  and  contraction 
produced  the  noise  of  explosion. 

38.  Pure  H  is  a  Gas  without  Color,  Odor,  or  Taste. 

—  li;  is  the  lightest  of  the  elements,  X4^  times  as  light  as 


28  HYDROGEN. 

air.  It  occurs  uncombined  in  coal-mines,  and  some  other 
places,  but  the  readiness  with  which  it  unites  with  other 
elements,  particularly  O,  prevents  its  accumulation  in 
large  quantities.  It  constitutes  two-thirds  of  the  volume 
of  the  gases  resulting  from  the  decomposition  of  water, 
and  one-ninth  of  the  weight.  Compute  the  latter  from  its 
symbol.  It  is  a  constituent  of  plants  and  animals,  and 
some  rocks.  Considering  the  volume  of  the  ocean,  the 
total  amount  of  H  is  large.  It  can  be  separated  from 
H2O  by  electrolysis  (page  44),  or  by  C,  as  in  the  manufac- 
ture of  water  gas  (page  78). 


Fig.  17. 

When  burned  with  O  it  forms  H2O.  Pure  O  and  H 
when  burning  give  great  heat,  but  little  light.  The  oxy- 
hydrogen  blow-pipe  (Fig.  17)  is  a  device  for  producing 
the  highest  temperatures  of  combustion.  It  has  O  in  the 
inner  tube  and  H  in  the  outer.  Why  would  it  not  be 
better  the  other  way?  These  unite  at  the  end,  and  are 
burned,  giving  great  heat.  A  piece  of  lime  put  into  the 
flame  gives  the  brilliant  Drummond  or  calcium  light. 


CHAPTER  IX. 

UNION  BY   WEIGHT. 

39.    In  the  Equation  — 

Zn  +  2  HC1  =  ZnCl2  +  2  H 
65  +     73     =    136    +    2 

65  parts  by  weight  of  Zn  are  required  to  liberate  2  parts  by  weight  of 
H;  or,  by  using  65*  Zn  with  73s  HC1,  we  obtain  2s  II.  If  twice  as 
much  Zn  (130s)  were  used,  4s  H  could  be  obtained,  with,  of  course, 
twice  as  much  HC1.  With  260s  Zn,  how  much  H  could  be  liberated? 
A  proportion  may  be  made  as  follows:  — 

Zn  given  :  Zn  required  : :  H  given  :  H  required.1 
65      :  260      ::          2     :  x. 

Solving,  we  have  8s  H. 

How  much  H  is  obtainable  by  using  5s  Zn,  as  in  the  experiment? 

To  avoid  error  in  solving  similar  problems,  the  best  plan  is  as 
follows :  — 


Zn  +  2  HC1  =  ZnCl2  +  2  II 
65  2 

5  '"    '<  'it 


65  :  5  : :  2  :  x 
65  x  =10 


The  equation  should  first  be  written ;  next,  the  atomic  or  molecular 
weights  which  you  wish  to  use,  and  only  those,  to  avoid  confusion ; 
then,  on  the  third  line,  the  quantity  of  the  substance  to  be  used,  with 
x  underneath  the  substance  wanted.  The  example  above  will  best 
show  this.  This  plan  will  prevent  the  possibility  of  error.  The  pro- 
portion will  then  be :  — 

a  given  :  a  required  : :  b  given  :  b  required. 
How  much  Zn  is  required  to  produce  30s  H  ? 

1  Given,  as  here  used,  means  the  weight  called  for  by  the  equation;  required 
that  called  for  by  the  question. 


30 


UNION  BY  WEIGHT. 


65 
x 

Solve :  — 


2  :  30  :  :  65  :  x 

2x=  1950 

x  =   975 


Ans.  975&  Zn. 


(1)  How  much  Zn  is  necessary  for  14&  H  ? 

(2)  How  many  pounds  of  Zn  are  necessary  for  3  pounds  of  H  ? 

(3)  How  many  grams' of  H  from  17&  of  Zn  ? 

(4)  How  many  tons  of  H  from  J  ton  of  Zn  ? 

Suppose  we  wish  to  find  how  much  chlorhydric  acid  —  pure  gas  — 
will  give  12s  H.  The  question  involves  only  HC1  and  H.  Arrange 
as  follows :  — 


2HCl=ZnCl2  +  2H 
73  2 

x  12 


H  giv. :  H  req. : :  HC1  giv. :  HC1  req. 
2      :      12     ::       73        •       x 

Ans.  438s  HC1. 


Solve:  — 


(1)  How  much  HC1  is  needed  to  produce  100*  H? 

(2)  How  much  H  in  10&  HC1? 

(3)  How  much  ZnCl2  is  formed  by  using  50*?  HC1?    The  question 
is  now  between  HC1  and  ZnCl2. 


Zn  +  2  HC1  =  ZnCl2  +  2  H 
73         136 
50  x 


Arrange  the  proportion,  and  solve. 


Suppose  we  have  generated  H  by  using  H2S04:  the  equation  is 
Zn  +  H2SO4  =  ZnSO4  +  2  H.  There  is  the  same  relation  as  before 
between  the  quantities  of  Zn  and  of  H,  but  the  H2SO4  and  ZnSO4  are 
different. 

How  much  H2SO4  is  needed  to  generate  12«  H?     . 


Make  the  proportion,  and  solve. 


2 
12 


Zn+H2S04  =  ZnS04 

98 

x 

Solve:  — 

(1)  How  much  H  in  200*  H2SO4? 

(2)  How  much  ZnSO4  is  produced  from  200*  H2SO4? 


UNION  BY   WEIGHT.  31 

(3)  How  much  H2SO4  is  needed  for  7£*  H  ? 

(4)  How  much  Zn  will  40«  H2SO4  combine  with? 

(5)  How  much  Fe  will  40^  H2SO4  combine  with?    See  page  25. 

(6)  How  much  PI  can  be  obtained  by  using  758  Fe  ? 

These  principles  apply  to  all  reactions.  Suppose,  for  example,  we 
wish  to  get  10s  of  O :  how  much  KC1O3  will  it  be  necessary  to  use  ? 
The  reaction  is :  —  > 


KC103  =  KC1  +  03 

122.5  48 

x  10 


48:  10::  122.5:* 


Ans.  25.5+K  KC1O3. 

The  pupil  should  be  required  to  make  up  problems  of  his  own, 
using  various  reactions,  and  to  solve  them. 


CHAPTER   X. 

CARBON. 

Examine  graphite,  anthracite  coal,  bituminous  coal,  cannel  coal, 
wood,  gas  carbon,  coke. 

4O.    Preparation  of  C. 

Experiment  26. —  Hold  a  porcelain  dish  or  a  plate  in  the  flame 
of  a  candle,  or  of  a  Bunsen  burner  with  the  openings  at  the  bottom 
closed.  After  a  minute  examine  the  deposit.  It  is  carbon,  i.e.  lamp- 
black or  soot,  which  is  a  constituent  of  gas,  or  of  the  candle.  Open 
the  valve  at  the  base  of  the  Bunsen  burner,  and  hold  the  deposit  in 
the  flame.  Does  the  C  gradually  disappear  ?  If  so,  it  has  been  burned 
to  CO2.  C  +  2  O  =  CO2.  Is  C  a  combustible  element  ? 

Experiment  27.  —  Ignite  a  splinter,  and  observe  the  combustion 
and  the  smoke,  if  any.  Try  to  collect  some  C  in  the  same  way  as 
before. 

With  plenty  of  O  and  high  enough  temperature,  all  the 
C  is  burned  to  CO2,  whether  in  gas,  candle,  or  wood. 
COa  is  an  invisible  gas.  The  porcelain,  when  held  in  the 
flame,  cools  the  C  below  the  point  at  which  it  burns,  called 
the  kindling-point,  and  hence  it  is  deposited.  The  greater 
part  of  smoke  is  unburned  carbon. 

Experiment  28.  —  Hold  an  inverted  dry  t.t.  or  receiver  over  the 
flame  of  a  burning  candle,  and  look  for  any  moisture  (H2O).  What 
two  elements  are  shown  by  these  experiments  to  exist  in  the  candle  ? 
The  same  two  are  found  in  wood  and  in  gas. 


CARBON. 


33 


Fig.  18. 


Experiment  29.  —  Put  into  a  small  Hessian  crucible  (Fig.   18) 
some  pieces  of  wood  2  or  3cm  long,  cover  with  sand,  and  heat  the 
crucible  strongly.     When  smoking  stops,  cool 
the  crucible,  remove  the  contents,  and  examine 
the  charcoal.     The  gases  have  been  driven  off 
from  the  wood,  and  the  greater  part  of  what 
is  left  is  C. 

Experiment  30.  —  Put  Is  of  sugar  into  a 
porcelain  crucible,  and  heat  till  the  sugar  is 
black.  C  is  left.  See  Experiment  5.  Re- 
move the  C  with  a  strong  solution  of  sodium 
hydrate  (page  208). 

41.  Allotropic    Forms.  —  Carbon 
is  peculiar  in  that  it  occurs  in  at  least 

three  allotropic,  i.e.  different,  forms,  all  having  different 
properties.  These  are  diamond,  graphite,  and  amorphous 
—  not  crystalline  —  carbon.  The  latter  includes  charcoal, 
lamp-black,  bone-black,  gas  carbon,  coke,  and  mineral  coal. 
All  these  forms  of  C  have  one  property  in  common ;  they 
burn  in  O  at  a  high  temperature,  forming  CO2.  This 
proves  that  each  is  the  element  C,  though  it  is  often  mixed 
with  some  impurities. 

Allotropy,  or  allotropism,  is  the  quality  which  an  element  often  has 
of  appearing  under  various  forms,  with  different  properties.  The  forms 
of  C  are  a  good  illustration. 

42.  Diamond  is  the  purest  C ;  but  even  this  in  burn- 
ing leaves  a  little  ash,  showing  that  it  is  not  quite  pure. 
It  is  a  rare  mineral,  found  in  India,  South  Africa,  and 
Brazil,  and  is  the  hardest  and  most  highly  refractive  to 
light  of  all  minerals.     Boron  is  harder.1     When  heated  in 
the  electric  arc,  at  very  high  temperatures,  diamond  swells 
and  turns  black. 

1  13,  nut  occurring  free,  is  uot  a  mineral. 


34  CARBON. 

43.  Graphite,  or  Plumbago,  is   One  of  the    Softest 
Minerals.  —  It  is  black  and  infusible,  and  oxidizes  only  at 
very  high  temperatures,  higher  than  the  diamond.    It  con- 
tains from  95  to  98  per  cent  C.     Graphite  is  found  in  the 
oldest  rock  formations,  in  the  United  States  and  Siberia. 
It  is  artificially  formed   in   the   iron  furnace.     Graphite 
is  employed  for  crucibles  where   great   heat  is  required, 
for  a  lubricant,  for   making   metal    castings,   and,  mixed 
with    clay,    for   lead-pencils.      It   is    often    called    black- 
lead. 

44.  Amorphous  Carbon    comprises   the  following  va- 
rieties. 

Charcoal  is  made  by  heating  wood,  for  a  long  time,  out 
of  contact  with  the  air.  The  volatile  gases  are  thus  driven 
off  from  the  wood ;  what  is  left  is  C,  and  a  small  quantity 
of  mineral  matter  which  remains  as  ash  when  the  coal  is 
burned. 

45.  Lamp-black  is  prepared  as  in  Experiment  26,  or 
by  igniting  turpentine  (C10H16),  naphtha,  and  various  oils, 
and  collecting  the  C  of  the  smoke.     It  is  used  for  making 
printers'  ink,    India   ink,  etc.      A  very  pure  variety  is 
obtained  from  natural  gas. 

Bone-black,  or  animal  charcoal,  is  obtained  by  distilling 
bones,  i.e.  by  heating  them  in  retorts  into  which  110  air  is 
admitted.  The  C  is  the  charred  residue. 

Gas  Carbon  is  formed  in  the  retorts  of  the  gas-house. 
See  page  182.  It  is  used  to  some  extent  in  electrical  work. 

46.  Coke  is  the  residue  left  after  distilling  soft  coal. 
It  is  tolerably  pure  carbon,  with    some  ash  and  a  little 
volatile  matter.     It  burns  without  flame. 


CARBON.  35 

47.  Mineral  Coal  is  fossilized  wood  or  other  vegetable 
matter.     Millions  of  years  ago  trees  and  other  vegetation 
covered  the  earth  as  they  do  to-day.     In  certain   places 
they  slowly  sank,  together  with  the  land,  into  the  interior 
of  the  earth,  were  covered  with   sand,  rock,  and  water, 
and  heated  from  the  earth's  interior.    A  slow  distillation 
took  place,  which  drove  off  some  of  the  gases,  and  con- 
verted vegetable  matter  into  coal.     All  the  coal  dug  from 
the  earth  represents  vegetable  life  of   a  former   period. 
Millions  of  years  were  required  for  the  transformation ; 
but  the  same  change  is  in  progress  now,  where  peat  beds 
are   forming  from  turf. 

Coal  is  found  in  all  countries,  the  largest  beds  being 
in  the  United  States.  From  the  nature  of  its  formation, 
coal  varies  much  in  purity. 

Anthracite,  or  hard  coal,  is  purest  in  carbon,  some 
varieties  having  from  90  to  95  per  cent.  This  represents 
most  complete  distillation  in  the  earth;  i.e.  the  gases  have 
mostly  been  driven  off.  It  is  much  used  in  New  England. 

48.  Bituminous,  or  soft   coal,   crocks  the  hands,  and 
burns  rapidly  with  much  flame  and  smoke.     The  greater 
part  of  the  coal  in  the  earth  is  bituminous.     It  represents 
incomplete    distillation.      Hence,  by  artificially  distilling 
it,  illuminating  gas  is  made.     See  page  180.    It  is  far  less 
pure  C  than  anthracite. 

49.  Cannel  Coal  is  a  variety  of  bituminous  coal  which 
can  be  ignited  like  a  candle.     This  is  because  so  many  of 
the  gases  are  still  left,  and  it  shows  cannel  to  be  less  pure 
C  than  bituminous  coal. 

50.  Lignite,"  Peat,    Turf,    etc.,    are    still    less    pure 
varieties  of  C.     Construct  a  table  of  the  naturally  occur- 
ring forms  of  this  element,  in  the  order  of  their  purity. 


36  CARBON. 

Carbon  forms  the  basis  of  all  vegetable  and  animal  life ; 
it  is  found  in  many  rocks,  mineral  oils,  asphaltum,  nat- 
ural gas,  and  in  the  air  as  CO2. 

51.  C  a  Reducing  Agent. 

Experiment  31.  —  Put  into  a  small  ignition-tube  a  mixture  of  4 
or  SK  of  powdered  copper  oxide  (CuO),  with  half  its  bulk  of  powdered 
charcoal.  Heat  strongly  for  ten  or  fifteen  minutes.  Examine  the 
contents  for  metallic  copper.  With  which  element  of  CuO  has  C 
united  ?  The  reaction  may  be  written  :  CuO  +  C  =  CO  +  Cu.  Com- 
plete and  explain. 

A  Reducing,  or  Deoxidizing,  Agent  is  a  substance 
which  takes  away  oxygen  from  a  compound.  C  is  the 
most  common  and  important  reducing  agent,  being  used 
for  this  purpose  in  smelting  iron  and  other  ores,  making 
water-gas,  etc. 

An  Oxidizing  Agent  is  a  substance  that  gives  up  its 
O  to  a  reducing  agent.  What  oxidizing  agent  in  the 
above  experiment? 

52.  C  a  Decolorizer. 

Experiment  32.  —  Put  3  or  4s  of  bone-black  into  a  receiver,  and 
add  10  or  15CC  of  cochineal  solution.  Shake  this  thoroughly,  covering 
the  bottle  with  the  hand.  Then  pour  the  whole  on  a  filter  paper, 
and 'examine  the  filtrate.  If  all  the  color  is  not  removed,  filter  again. 
What  property  of  C  is  shown  by  this  experiment  ?  Any  other  color- 
ing solution  may  be  tried. 

The  decolorizing  power  of  charcoal  is  an  important 
characteristic.  Animal  charcoal  is  used  in  large  quan- 
tities for  decolorizing  sugar.  The  coloring  matter  is 
taken  out  mechanically  by  the  C,  there  being  no  chemi- 
cal action. 


CARBON.  37 

53.  C  a  Disinfectant. 

Experiment  33.  —  Repeat  the  previous  experiment,  adding  a  solu- 
tion of  H2S,  i.e.  hydrogen  sulphide,  in  water,  instead  of  cochineal  solu- 
tion. See  page  120.  Note  whether  the  bad  odor  is  removed.  If  not, 
repeat. 

Charcoal  has  the  property  of  absorbing  large  quantities 
of  many  gases.  Ill-smelling  and  noxious  gases  are  con- 
densed in  the  pores  of  the  C ;  O  is  taken  in  at  the  same 
time  from  the  air,  and  these  gases  are  there  oxidized  and 
rendered  odorless  and  harmless.  For  this  reason  charcoal 
is  much  used  in  hospitals  and  sick-rooms,  as  a  disinfectant. 
This  property  of  condensing  O,  as  well  as  other  gases,  is 
shown  in  the  experiment  below. 

54.  C    an    Absorber  of    Gases    and    a    Retainer   of 
Heat. 

Experiment  34.  —  Put  a  piece  of  phosphorus  of  the  size  of  a  pea, 
and  well  dried,  on  a  thick  paper.  Cover  it  well  with  bone-black,  and 
look  for  combustion  after  a  while.  O  has  been  condensed  from  the 
air,  absorbed  by  the  C,  and  thus  communicated  to  the  P.  Burn  all 
the  P  at  last. 


CHAPTER   XL 
VALENCE. 

55.  The  Symbols    NaCl   and   MgCl3    Differ    in   Two 

Ways.  —  What  are  they  ?  Let  us  see  why  the  atom  of 
Mg  unites  with  two  Cl  atoms,  while  that  of  Na  takes  but 
one.  If  the  atoms  of  two  elements  attract  each  other,  there 
must  be  either  a  general  attraction  all  over  their  surfaces, 
or  else  some  one  or  more  points  of  attraction.  Suppose  the 
latter  to  be  true,  each  atom  must  have  one  or  more  poles 
or  bonds  of  attraction,  like  the  poles  of  a  magnet.  Differ- 
ent elements  differ  in  their  number  of  bonds.  Na  has  one, 
which  may  be  written  graphically  Na-;  Cl  has  one,  -Cl. 
When  Na  unites  with  Cl,  the  bonds  of  each  element  bal- 
ance, as  follows :  Na  -  Cl.  The  element  Mg,  however,  has 
two  such  bonds,  as  Mg=  or  -Mg-.  When  Mg  unites 
with  Cl,  in  order  to  balance,  or  saturate,  the  bonds,  it  is 

Cl 
evident  that  two  atoms  of  Cl  must  be  used,  as  Mg  =  ™'  or 

Cl-Mg-Cl,  or  MgCl2. 

A  compound  or  an  element,  in  order  to  exist,  must  have 
no  free  bonds.  In  organic  chemistry  the  exceptions  to 
this  rule  are  very  numerous,  and,  in  fact,  we  do  not  know 
that  atoms  have  bonds  at  all ;  but  we  can  best  explain  the 
phenomena  by  supposing  them,  and  for  a  general  state- 
ment we  may  say  that  there  must  be  no  free  bonds.  In 
binaries  the  bonds  of  each  element  must  balance. 

56.  The  Valence,  Quantivalence,  of   an   Element  is 
its  Combining  Power  Measured  by  Bonds.  —  H,  having 


VALENCE.  39 

the  least  number  of  bonds,  one,  is  taken  as  the  unit.  Va- 
lence has  always  to  be  taken  into  account  in  writing  the 
symbol  of  a  compound.  It  is  often  written  above  and 
after  the  elements,  as  K1,  Mgn. 

An  element  having  a  valence  of  one  is  a  monad  ;  of  two, 
a  dyad;  three,  a  triad;  four,  tetrad;  five,  pentad;  six, 
hexad,  etc.  It  is  also  said  to  be  monovalent,  di-  or  bi- 
valent, etc.  This  theory  of  bonds  shows  why  an  atom 
cannot  exist  alone.  It  would  have  free  or  unused  bonds, 
and  hence  must  combine  with  its  fellow  to  form  a  mole- 
cule, in  case  of  an  element  as  well  as  in  that  of  a  com- 
pound. This  is  illustrated  by  these  graphic  symbols  in 
which  there  are  no  free  bonds:  H-H,  O  =  O,  N=N,  C  =  C. 
A  graphic  symbol  shows  apparent  molecular  structure. 

After  all,  how  do  we  know  that  there  are  twice  as  many 
Cl  atoms  in  the  chloride  of  magnesium  as  in  that  of  so- 
dium ?  The  compounds  have  been  analyzed  over  and  over 
again,  arid  have  been  found  to  correspond  to  the  symbols 
MgCl2  and  NaOl.  This  will  be  better  understood  after 
studying  the  chapter  on  atomic  weights.  In  writing  the 
symbol  for  the  union  of  H  with  O,  if  we  take  an  atom  of 
each,  the  bonds  do  not  balance,  H  -  =  O,  the  former  having 
one ;  the  latter,  two.  Evidently  two  atoms  of  H  are  needed, 

TT 

as  H  -  O  -  H,  or  rr  =  O,  or  H2O.     In  the  union  of  Zn  and 

O,  each  has  two  bonds;  hence  they  unite  atom  with  atom, 
Zn  =  O,  or  ZnO. 

Write  the  graphic  and  the  common  symbols  for  the  union 
of  H1  and  Cl1;  of  K1  and  Br1 ;  Ag1  and  O11;  Na1  and  Su; 
H1  and  Pm.  Study  valences,  page  12.  It  will  be  seen 
that  some  elements  have  a  variable  quantivalence.  Sn  has 
either  2  or  4 ;  P  has  3  or  5.  It  usually  varies  by  two  for 
a  given  element,  as  though  a  pair  of  bonds  sometimes 


40  VALENCE. 

saturated  each  other;  e.g.  =Sn=,  a  quantivalence  of  4, 
and  'Sn=,  a  quantivalence  of  2.  There  are,  therefore, 
two  oxides  of  tin,  SnO  and  SnO2,  or  Sn  =  O  and  O  =  Sn  =  O. 
Write  symbols  for  the  two  chlorides  of  tin ;  two  oxides  of 
P  (page  12)  ;  two  oxides  of  arsenic. 

The  chlorides  of  iron  are  FeCl2  and  Fe2Cl6.     In  the  lat- 
ter, it  might  be  supposed  that  the  quantivalence  of  Fe  is 
3,  but  the  graphic  symbol  shows  it  to  be  4.     It  is  called  a 
pseudo-triad,  or   false    triad.     Cr  and  Al 
i       '  are  also  pseudo-triads. 

Cl-Fe-Fe-Cl.  .       „  .  ,  £  . 

'       '  Write  formula  for  two  oxides  of  iron ; 

the  oxide  of  Al. 

57.  A  Radical  is  a  Group  of  Elements  which  has  no 
separate  existence,  but  enters  into  combination  like  a  sin- 
gle atom;'  e.g.  (NO3)  in  the  compounds  HNO3  or  KNO3; 
(SO4)  in  H2SO4.  In  HNO3the  radical  has  a  valence  of  1, 
to  balance  that  of  H,  H-(NO3).  In  H2SO4,  what  is  the 
valence  of  (SO4)  ?  Give  it  in  each  of  these  radicals,  not- 
ing first  that  of  the  first  element:  K(NO3),  Na2(SO4), 
Na2(C03),  K(C10s),  H3(P04),  Ca3(PO4)2,  Na4(SiO4). 

Suppose  we  wish  to  know  the  symbol  for  calcium 
phosphate.  Ca  and  PO4  are  the  two  parts.  In  H3(PO4) 
the  radical  is  a  triad,  to  balance  H3.  Ca  is  a  dyad, 
Ca  =  =  (PO4).  The  least  common  multiple  of  the  bonds' 
(2  and  3)  is  6,  which,  divided  by  2  (no.  Ca  bonds),  gives 
3  (no.  Ca  atoms  to  be  taken).  6-3  (no.  (PO4)  bonds) 
gives  2  (no.  PO4  radicals  to  be  taken).  Hence  the  sym- 
bol Ca3(PO4)2.  Verify  this  by  writing  graphically. 

Write  symbols  for  the  union  of  Mg  and  (SO4),  Na  and 
(PO4),  Zn  and  (NO8),  K  and  (NO3),  K  and  (SO4),  Mg 
and  (PO4),  Fe  and  (SO4)  (both  valences  of  Fe),  Fe  and 
(NO3),  taking  the  valences  of  the  radicals  from  HNO3, 
*  H3PO4. 


CHAPTER   XII. 
ELECTRO-CHEMICAL   RELATION  OF  ELEMENTS. 

58.  Examine  untarnished  pieces  of  iron,  silver,  nickel, 
lead,  etc. ;  also  quartz,  resin,  silk,  wood,  paper.  Notice 
that  from  the  first  four  light  is  reflected  in  a  different  way 
from  that  of  the  others.  This  property  of  reflecting  light 
is  known  as  luster.  Metals  have  a  metallic  luster  which  is 
peculiar  to  themselves ;  and  this,  for  the  present,  may  be 
regarded  as  their  chief  characteristic.  Are  they  at  the 
positive  or  negative  end  of  the  list?  See  page  43.  How 
is  it  with  the  non-metals?  This  arrangement  has  a  sig- 
nificance in  chemistry  which  we  must  now  examine.  The 
three  appended  experiments  show  how  one  metal  can  be 
withdrawn  from  solution  by  a  second,  this  second  by  a 
third,  the  third  by  a  fourth,  and  so  on.  For  expedition, 
three  pupils  can  work  together  for  the  three  following  ex- 
periments, each  doing  one,  and  examining  the  results  of 
the  others. 

,     59.    Deposition  of  Silver. 

Experiment  35.  —  Put  a  ten-cent  Ag  coin  into  an  evaporating-dish, 
and  pour  over  it  a  mixture  of  5CC  HNO3  and  10CC  H2O.  Warm  till 
all,  or  nearly  all,  the  Ag  dissolves.  Remove  the  lamp. 
'•  3Ag  +  4HNO3  =  3AgNO3+2H2O  +  lSrO.  Then  add  10CC  H2O, 
and  at  once  put  in  a  short  piece  of  Cu  wire,  or  a  cent.  Leave  till 
quite  a  deposit  appears,  then  pour  off  the  liquid,  wash  the  deposit 
thoroughly,  and  remove  it  from  the  coin.  See  whether  the  metal 
resembles  Ag.  2  AgNO3  +  Cu  =  ? 


42          ELECTRO-CHEMICAL   RELATION   OF   ELEMENTS. 

60.  Deposition  of  Copper. 

Experiment  36.  —  Dissolve  a  cent  or  some  Cu  turnings  in  dilute 
HNO3,  as  in  Experiment  35,  and  dilute  the  solution.  3  Cu  +  8  HNO3 
=  3  Cu(NO3)2  +  4  H2O  +  2  NO. 

Then  put  in  a  clean  strip  of  Pb,  and  set  aside  as  before,  examining 
the  deposit  finally.  Cu(NO3)2  +  Pb  =  ? 

61.  Deposition  of  Lead. 

Experiment  37.  —  Perform  this  experiment  in  the  same  manner  as 
the  two  previous  ones,  dissolving  a  small  piece  of  Pb,  and  using  a 
strip  of  Zn  to  precipitate  the  Pb.  3  Pb  +  8  HNO3  =  3  Pb  (NO3)2  + 
4  H20  +  2  NO.  Pb  (N03)2  +  Zn  =  ? 

62.  Explanation.  —  These  experiments  show  that  Cu 
will  replace  Ag  in  a  solution  of  AgNO3,  that  Pb  will  replace 
and  deposit  Cu  from  a  similar  compound,  and  that  Zn  will 
deposit  Pb  in  the  same  way.     They  show  that  the  affinity 
of  Zn  for  (NO3)  is  stronger  than  either  Ag,  Cu,  or  Pb. 
We  express  this  affinity  by  saying  that  Zn  is  the  most 
positive  of  the  four  metals,  while  Ag  is  the  most  nega- 
tive.    Cu  is  positive  to  Ag,  but  negative  to  Pb  and  Zn. 
Which  of  the  four  elements  are  positive  to  Pb,  and  which 
negative?     Mg  would  withdraw  Zn  from  a  similar  solu- 
tion, and  be  in   its  turn  withdrawn   by  Na.     The   table 
on  page  43  is  founded  on  this  relation.     A  given  element 
is  positive  to   every   element   above   it  in  the  list,  and 
negative  to  all  below  it. 

Metals  are   usually  classed   as   positive,  non-metals   as 
negative.     Each  in  union  with  O  and  H  gives  rise  to  a    • 
very  important   class   of   compounds,  —  the    negative    to 
acids,  the  positive  to  bases. 

In  the  following,  note  whether  the  positive  or  the  nega- 
tive element  is  written  first:  HC1,  Na2O,  As2S3,  MgBr2, 
Ag2S.  Na2SO4  is  made  up  of  two  parts,  Na2  being  posi- 


ELECTROCHEMICAL   RELATION   OF   ELEMENTS. 


43 


g  W 

a  o 


-  M" 


'i«  ^ 

§)0 


8 


ORDER. 

f  Oxygen 
Sulphur 
Nitrogen 
Fluorine 
Chlorine 
Bromine 
Iodine 
Phosphorus 
Arsenic 
Carbon 
Silicon 

Hydrogen 

r  Gold 

Platinum 
Mercury 
Silver 
Copper 
Tin 
Lead 
Iron 
Zinc 

Aluminium 
Magnesium 
Calcium 
Sodium 
.  Potassium 


tive,  the  radical  SO4  negative.  Like 
elements,  radicals  are  either  positive 
or  negative.  In  the  following,  separate 
the  positive  element  from  the  negative 
radical  by  a  vertical  line :  Na2CO3, 
NaNO3,  ZnSO4,  KC1O3. 

The  most  common  positive  radical 
is  NH4,  ammonium,  as  in  NH4C1.  It 
always  deports  itself  as  a  metal.  The 
commonest  radical  is  the  negative 
OH,  called  hydroxyl,  from  hydrogen- 
oxygen.  Take  away  H  from  the  sym- 
bol of  water,  H-O-H,  and  hydroxyl 
-(OH)  with  one  free  bond  is  left.  If 
an  element  takes  the  place  of  H,  i.e. 
unites  with  OH,  the  compound  is 
called  a  hydrate.  KOH  is  potassium 
hydrate.  Name  NaOH,  Ca(OH)2, 
NH4OH,  Zn(OH>,  A12(OH)6.  Is 
the  first  part  of  each  symbol  above 
positive  or  negative  ? 

H  has  an  intermediate  place  in  the 
list.  It  is  a  constituent  of  both  acids 
and  bases,  and  of  the  neutral  sub- 
stance, water. 


CHAPTER  XIII. 


H 


ELECTROLYSIS. 

The  following  experiment  is  to  be  performed  only  by 
the  teacher,  but  pupils  should  make  drawings  and  ex- 
plain. 

63.    Decomposition  of  Water. 

Experiment  38.  —  Arrange  "in  series"  two  or  more  cells  of  a 
Bunsen  battery  (Physics,  page  164), *  and  attach  the  terminal  wires  to 
an  electrolytic  apparatus  (Fig.  19)  filled  with  water 
made  slightly  acid  with  H2SO4.  Construct  a  dia- 
gram of  the  apparatus,  marking  the  Zn  in  the 
liquid  +,  since  it  is  positive,  and  the  C,  or  other 
element,  — .  Mark  the  electrode  attached  to  the 
Zn  — ,  and  that  attached  to  the  C  +  ;  positive  elec- 
tricity at  one  end  of  a  body  commonly  implies  neg- 
ative at  the  other.  Opposites  attract,  while  like 
electricities  repel  each  other.  These  analogies  will 
aid  the  memory.  At  the  +  electrode  is  the  —  ele- 
ment of  H2O,  and  at  the  —  electrode  the  +  element. 
Xote,  page  43,  whether  II  or  O  is  positive  with  ref- 
erence to  the  other,  and  write  the  symbol  for  each 
at  the  proper  electrode.  Compare  the  diagram 
with  the  apparatus,  to  verify  your  conclusion. 
Why  does  gas  collect  twice  as  fast  at  one  electrode 
as  at  the  other  ?  What  does  this  prove  of  the  com- 
position of  water?  When  filled,  test  the  gases  in  each  tube,  for  O  and 
H,  with  a  burning  stick.  Electrical  analysis  is  called  electrolysis. 

If  a  solution  of  NaCl  be  electrolyzed,  which  element 
will  go  to  the  -j-pole?  Which,  if  the  salt  were  K2SO4? 

1  References  are  made  in  this  book  to  Gage's  Introduction  to  Physical  Science. 


Fig.  19. 


ELECTROLY 

Explain  these  reactions  in  the  electrolysis  of  that  salt. 
K2SO4  ===  K2  -f  SO3  +  O.  SO4  is  unstable,  and  breaks  up 
into  SO3  and  O.  Both  K  and  SO3  have  great  affinity  for 
water.  K2  +  2  H2O  =  2  KOH  +  H2.  SO3  +  H2O  -  H2SO4. 

The  base  KOH  would  be  found  at  the  —  electrode,  and 
the  acid  H2SO4  at  the  +  electrode. 

The  positive  portion,  K,  uniting  with  H2O  forms  a  base ; 
the  negative  part,  SO3,  with  H2O  forms  an  acid.  Of  what 
does  this  show  a  salt  to  be  composed? 

64.  Conclusions.  —  These  experiments  show  (1)  that 
at  the  +  electrode  there  always  appears  the  negative  ele- 
ment, or  radical,  of  the  compound,  and  at  the  —electrode 
the  positive  element ;  (2)  that  these  elements  unite  with 
those  of  water,  to  make,  in  the  former  case,  acids,  in  the 
latter,  bases ;  (3)  that  acids  and  bases  differ  as  negative 
and  positive  elements  differ,  each  being  united  with  O  and 
H,  arid  yet  producing  compounds  of  a  directly  opposite 
character ;  (4)  that  salts  are  really  compounded  of  acids 
and  bases.  This  explains  why  salts  are  usually  inactive 
and  neutral  in  character,  while  acids  and  bases  are  active 
agents.  Thus  we  see  why  the  most  positive  or  the  most 
negative  elements  in  general  have  the  strongest  affinities, 
while  those  intermediate  in  the  list  are  inactive,  and  have 
weak  affinities  ;  why  alloys  of  the  metals  are  weak  com- 
pounds ;  why  a  neutral  substance,  like  water,  has  such  a 
weak  affinity  for  the  salts  which  it  holds  in  solution  ;  and 
why  an  aqueous  solution  is  regarded  as  a  mechanical  mix- 
ture rather  than  a  chemical  compound.  In  this  view,  the 
division  line  between  chemistry  and  physics  is  not  a  dis- 
tinct one.  These  will  be  better  understood  after  study- 
ing the  chapters  on  acids,  bases  and  salts. 


CHAPTER  XIV. 

UNION  BY   VOLUME. 

65.  Avogadro's  Law  of  Gases.  —  Equal  volumes  of 
all  gases,  the  temperature  and  pressure  being  the  same, 
have  the  same  number  of  molecules.  This  law  is  the 
foundation  of  modern  chemistry.  A  cubic  centimeter  of 
O  has  as  many  molecules  as  a  cubic  centimeter  of  H,  a 
liter  of  N  the  same  number  as  a  liter  of  steam,  under  sim- 
ilar conditions.  Compare  the  number  of  molecules  in 
51  of  N2O  with  that  in  101  Cl.  7CC  vapor  of  I  to  6"  vapor 
of  S.  The  half-molecules  of  two  gases  have,  of  course, 
the  same  relation  to  each  other,  and  in  elements  the  half- 
molecule  is  usually  the  atom. 

The  molecular  volumes  —  molecules  and  the  surround- 
ing space  —  of  all  gases  must  therefore  be  equal,  as  must 
the  half-volumes.  Notice  that  this  law  applies  only  to 
gases,  not  to  liquids  or  solids.  Let  us  apply  it  to  the  ex- 
periment for  the  electrolysis  of  water.  In  this  we  found 
twice  as  much  H  by  volume  as  O.  Evidently,  then,  steam 
has  twice  as  many  molecules  of  H  as  of  O,  and  twice  as 
many  half-molecules,  or  atoms.  If  the  molecule  has  one 
atom  of  O,  it  must  have  two  of  H,  and  the  formula  will 
be  H2O. 

Suppose  we  reverse  the  process  and  synthesize  steam, 
which  can  be  done  by  passing  an  electric  spark  through 
a  mixture  of  H  and  O  in  a  eudiometer  over  mercury;  we 
should  need  to  take  twice  as  much  H  as  O.  Now  when 
2CC  of  H  combine  thus  with  lco  of  O,  only  2°°  of  steam 
are  produced.  Three  volumes  are  condensed  into  two 


UNION  BY  VOLUME.  47 

volumes,  and  of  course  three  molecular  volumes  into  two, 
three  atomic  volumes  into  two.     This  may  be  written  as 

follows  :  — 


H  +  H  +  O  =  H,O. 

This  is  a  condensation  of  one-third. 

If  21  of  chlorhydric  acid  gas  be  analyzed,  there  will 
result  I1  of  H  and  I1  of  Cl.  The  same  relation  exists 
between  the  molecules  and  the  atoms,  and  the  reaction 

is:  — 


HCl  =  H  +  Cl. 

Reverse  the  process,  and  I1  of  H  unites  with  I1  of  Cl  to 
produce  21  of  the  acid  gas  ;  there  is  no  condensation,  and 
the  symbol  is  HC1.  In  seven  volumes  HC1  how  many 
of  each  constituent  ? 

The  combination  of  two  volumes  of  H  with  one  volume 
of  S  is  found  to  produce  two  volumes  of  hydrogen  sul- 
phide. Therefore  two  atoms  of  H  combine  with  one  of  S 
to  form  a  molecule  whose  symbol  is  H2S. 

n  +  n  +  n-izu 

H  +  H  +  S  =  HaS. 

What  is  the  condensation  in  this  case  ? 

PROBLEMS. 

(1)  How  many  liters  of   S  will  it  take  to  unite  with  41  of  H?     How 
much  H2S  will  be  formed  ? 

(2)  How  many  liters  of  H  will  it  take  to  combine  with  61  of  S  ?     How 
much  H2S  results  ? 

(3)  In  61  H2S  how  many  liters  H,  and  how  much  S  ?     Prove. 

(4)  In  four  volumes  H2S  how  many  volumes  of  each  constituent? 

(^)  If  three  volumes  of  H  be  mixed  with  two  volumes  of  S,  so  as  to 
make  H2S,  how  much  will  be  formed  ?  How  much  of  either  element  will 
be  left? 


48  UNION  BY  VOLUME. 

An  analysis  of  2°°  of  ammonia  gives  lcc  N  and  3°°  H, 
The  symbol  must  then  be  NH3,  the  reaction,  — 


NH3  =  N  +  H  +  H  +  H. 
What  condensation  in  the  synthesis  of  NH3? 

In  12CC  NH3  how  many  cubic  centimeters  of  each  element?  In  2£cc? 
How  much  H  by  volume  is  required  to  combine  with  nine  volumes  of  N  ? 
How  many  volumes  of  NH3  are  produced  ? 

In  elements  that  have  not  been  weighed  in  the  gaseous 
state,  as  C,  the  evidence  of  atomic  volume  is  not  direct, 
but  we  will  assume  it.  Thus  two  volumes  of  marsh  gas 
would  separate  into  one  of  C  and  four  of  H.  What  is 
its  symbol  and  supposed  condensation?  Two  volumes 
of  alcohol  vapor  resolve  into  two  of  C,  six  of  H,  and  one 
of  O.  What  is  its  symbol  ?  its  condensation  ? 

The  symbol  itself  of  a  compound  will  usually  show 
what  its  condensation  is;  e.g.  HC1,  HBr,  HF,  etc.,  have 
two  atoms  ;  hence  there  will  be  110  shrinkage.  In  H2O, 
SO2,  GO2,  the  molecule  has  three  atoms  condensed  into 
the  space  of  two,  or  one-third  shrinkage.  In  NH3  four 
volumes  are  crowded  into  the  space  of  two,  a  condensation 
of  one-half. 

P,  As,  Hg,  Zn,  have  exceptional  atomic  volumes.  See 
page  112. 


CHAPTER   XV. 
ACIDS  AND  BASES. 

66.  What  Acids  Are. 

Experiment  39.  —  Pour  a  few  drops  of  chlorhydric  acid,  HC1,  into 
a  clean  evaporating-dish.  Add  5°°  H2O,  and  stir.  Touch  a  drop  to  the 
tongue,  noting  the  taste.  Dip  into  it  the  end  of  a  piece  of  blue  litmus 
paper,  and  record  the  result.  Thoroughly  wash  the  dish,  then  pour  in 
a  few  drops  of  nitric  acid,  HNO3,  and  5°°  H2O,  and  stir.  Taste,  and 
test  with  blue  litmus.  Test  in  the  same  way  sulphuric  acid,  H2SO4. 
Name  two  characteristics  of  an  acid.  In  a  vertical  line  write  the  for- 
mulae of  the  acids  above.  What  element  is  common  to  them  all?  Is 
the  rest  of  the  formula  positive  or  negative  ? 

67.  An  Acid  is  a  substance  composed  of  H  and  a  nega- 
tive element  or  radical.     It  has  usually  a  sour  taste,  and 
turns  blue  litmus  red.     Litmus  is  a  vegetable  extract  ob- 
tained from  lichens  in  Southern  Europe.     Acids  have  the 
same  action  on  many  other  vegetable  pigments.     Are  the 
following  acid  formulas,  and  why?     H2SO3,  HBr,  HNO^ 
H3PO3,  H4SiO4.     Most  acids  have  0  as  well  as  H.     Com- 
plete the  symbols  for  acids  in  the  following  list,  and  name 
them,  from  the  type  given :  — 


HC1,  chlorhydric  acid. 


Br, 

?  Br? 
a  ?  I? 


H3PO4,  phosphoric  acid. 


HN0,  nitric  acid. 


H3P03,  phosphorous  acid, 


50  ACIDS   AND   BASES. 

Complete  these  equations :  — 


H2C03-H20  = 


2HN03-H2O  =  f 
2HN02-H2O  =  ? 
2  H3AsO4-3H2O=? 


Are  the  products  in  each  case  metallic  or  non-metallic  oxides  ?  They 
are  called  anhydrides.  Notice  that  each  is  formed  by  the  withdrawal  of 
water  from  an  acid.  Kevem  the  equations ;  as,  SO3  +  H2O  =  ? 

68.  An  Anhydride  is  what  remains   after  water  has 
been  removed  from  an  acid ;  or,  it  is  the  oxide  of  a  non- 
metallic    element,  which,  united    with    water,    forms   an 
acid.     SO2  is   sulphurous   anhydride,   SO3  sulphuric   an- 
hydride,  the   ending   ic  meaning   more    O,    or    negative 
element,  than  ous.     Name  the  others  above. 

Anhydrides  were  formerly  called  acids,  —  anhydrous 
acids,  in  distinction  from  hydrated  ones,  as  CO2  even 
now  is  often  called  carbonic  acid. 

Experiment  40.  —  Hold  a  piece  of  wet  blue  litmus  paper  in  the 
fumes  of  SO2,  and  note  the  acid  test.  Try  the  same  with  dry  litmus 
paper. 

Experiment  41.  —  Burn  a  little  S  in  a  receiver  of  air  containing 
10CC  H2O,  and  loosely  covered,  as  in  the  O  experiment.  Then  shake 
to  dissolve  the  SO2.  H2O  +  SO2  =  H2S03.  Apply  test  paper. 

69.  Naming1   Acids.  —  Compare   formulae    H2SO3   and 
H2SO4.     Of  two  acids  having  the  same  elements,  the  name 
of  the  one  with  least   O,  or  negative   element,  ends  in 
ous,  the  other  in  ic.     H2S03  is  sulphurous  acid ;  H2SO4, 
sulphuric  acid.     Name  H3PO4  and  H3PO3 ;  H3AsOs  and 
H3AsO4;  HNO2and  HN03. 

If  there  are  more  than  two  acids  in  a  series,  the  pre- 
fixes hypo,  less,  and  per,  more,  are  used.  The  following  is 
such  a  series:  HC1O,  HC102,  HC1O8,  HC1O4. 

HC1O8  is  chloric  acid;  HC1O2,  chlonnw;  HC10,  hypo- 


ACIDS   AND  BASES.  51 

chlorous  ;  HC1O4  perchloric.  Hypo  means  less  of  the  neg- 
ative element  than  ous ;  per  means  more  of  the  negative 
element  than  ic.  Name:  H3PO4  («?),  H3PO3,  H3PO2. 
Also  HBrO  (HBrO2  does  not  exist),  HBrO3  (w),  HBrO4. 
What  are  the  three  most  negative  elements  ?  Note  their 
occurrence  in  the  three  strongest  and  most  common  acids. 
Hereafter  note  the  names  and  symbols  of  all  the  acids  you 
see. 

7O.    What  Bases  Are. 

Experiment  42.  —  Put  a  few  drops  of  NH4OH  into  an  evaporating- 
dish.  Add  5CC  H2O,  and  stir.  Taste  a  drop.  Dip  into  it  a  piece  of 
red  litmus  paper,  noting  the  effect.  Cleanse  the  dish,  and  treat  in  the 
same  way  a  few  drops  NaOH  solution,  recording  the  result.  Do  the 
same  with  KOH.  Acid  stains  on  the  clothing,  with  the  exception  of 
those  made  by  HNO3,  may  be  removed  by  NH4OH.  H2SC>4,  however, 
rapidly  destroys  the  fiber  of  the  cloth. 

Name  two  characteristics  of  a  base.  In  the  formulse  of 
those  bases,  what  two  common  elements?  Name  the  radi- 
cal. Compare  those  symbols  with  the  symbol  for  water, 
HOH.  Is  (OH)  positive  or  negative  ?  Is  the  other  part 
of  each  formula  positive  or  negative  ?  What  are  two  con- 
stituents, then,  of  a  base?  Bases  are  called  hydrates. 
Write  in  a  vertical  line  five  positive  elements.  Note  the 
valence  of  each,  and  complete  the  formula  for  its  base. 
Affix  the  names.  Can  you  see  any  reason  why  the  three 
bases  above  given  are  the  strongest  ?  See  page  43. 

Taking  the  valences  of  Cr  and  Fe,  write  symbols  for 
two  sets  of  hydrates,  and  name  them.  Try  to  recognize 
and  name  every  base  hereafter  met  with. 

A  Base  is  a  substance  which  is  composed  of  a  metal, 
or  positive  radical,  and  OH.  It  generally  turns  red  lit- 
mus blue,  and  often  has  an  acrid  taste. 


52  ACIDS   AND   BASES. 

An  Alkali  is  a  base  which  is  readily  soluble  in  water. 
The  three  principal  alkalies  are  NH4OH,  KOH,  and  NaOH. 

Alkali  Metals  are  those  which  form  alkalies.  Name 
three. 

An  Alkaline  Reaction  is  the  turning  of  red  litmus 
blue. 

An  Acid  Reaction  is  the  turning  of  blue  litmus  red. 

Experiment  43.  —  Pour  5CC  of  a  solution  of  litmus  in  water,  into  a 
clean  t.t.  or  small  beaker.  Pour  2  or  3CC  of  HC1  into  an  evaporating- 
dish,  and  the  same  quantity  of  NH4OH  into  another  dish.  Take  a 
drop  of  the  HC1  on  a  stirring-rod  and  stir  the  litmus  solution  with  it. 
Note  the  acid  reaction.  Clean  the  rod,  and  with  it  take  a  drop  (or 
more  if  necessary)  of  NH4OH,  and  add  this  to  the  red  litmus  solu- 
tion, noting  the  alkaline  reaction. ,  Experiment  in  the  same  way  with 
the  two  other  principal  acids  and  the  two  other  alkalies. 

Litmus  paper  is  commonly  used  to  test  these  reactions,  and  hereafter 
whenever  the  term  litmus  is  employed  in  that  sense,  the  test-paper  should 
be  understood.  This  paper  can  he  prepared  by  dipping  unglazed  paper 
into  a  strong  aqueous  solution  of  litmus. 


CHAPTER   XVI. 

SALTS. 

71.  Acids  and  Bases  are  usually  Opposite  in  Char- 
acter. —  When  two  forces  act  in  opposition  they  tend  to 
neutralize  each  other.      We   may  see  an  analogy  to  this 
in  the  union  of  the  two  opposite  classes  of  compounds, 
acids  and  bases,  to  form  salts. 

72.  Neutralization. 

Experiment  44.  —  Put  into  an  evaporating-dish  5CC  of  NaOH  solu- 
tion (page  208)  .  Add  HC1  to  this  from  a  t.t.,  a  few  drops  at  a  time,  stir- 
ring the  mixture  with  a  glass  rod  (Fig.  20),  and 
testing  it  with  litmus  paper,  until  the  liquid  is 
neutral,  i.e.  will  not  turn  the  test  paper  from 
blue  to  red,  or  red  to  blue.  Test  with  both  col- 
ors. If  it  turns  blue  to  red,  too  much  acid  has 

been   added; 

if  red  to  blue, 

too     much 

base.    When 

it     is    very 

nearly     neu- 

tral, add  the 

Fig.  2O.  ,     TT,,, 

reagent,  HC1 

or  NaOH,  a  drop  at  a  time  with  the  stirring-rod.  It  must  be  absolutely 
neutral  to  both  colors.  Evaporate  the  water  by  heating  the  dish  over 
asbestus  paper,  wire  gauze,  or  sand,  in  an  iron  plate  (Fig.  21)  till  the 
residue  becomes  dry  and  white.  Cool  the  residue,  taste,  and  name  it. 
The  equation  is  :  HC1  +  NaOH  =  NaCl  +  HOH  or  H2O.  Note  which 
elements,  positive  or  negative,  change  places.  Why  was  the  liquid 
boiled  ?  The  residue  is  a  type  of  a  large  class  of  compounds,  called  salts. 

Experiment  45.  —  Experiment  in  the  same  way  with  KOH  solu- 


81. 


54  SALTS. 

tion  and  H2SO4,  applying  the  same  tests.      H2SO4  +  2  KOH  =  K2SO4  + 
2  HOH.     What  is  the  solid  product  ? 

Experiment  46.  —  Neutralize  NH4OH  with  HNO3,  evaporate,  ap- 
ply the  tests,  and  write  the  equation.  Write  equations  for  the  combi- 
nation of  NaOH  and  H2SO4 ;  NaOH  and  HNO3 ;  KOH  and  HC1 ;  KOH 
and  HNO3 ;  NH4OH  and  HC1 ;  NH4OH  and  H2SO4.  Describe  the  ex- 
periment represented  by  each  equation,  and  be  sure  you  can  perform  it 
if  asked  to  do  so.  What  is  the  usual  action  of  a  salt  on  litmus? 
How  is  a  salt  made  ?  What  else  is  formed  at  the  same  time  ?  Have 
all  salts  a  saline  taste  ?  Does  every  salt  contain  a  positive  element  or 
radical  ?  A  negative  ? 

73.  A  Salt  is  the  product  of  the  union  of  a  positive 
and  a  negative  element  or  radical ;  it  may  be  made  by 
mixing  a  base  and  an  acid. 

The  salt  KI  represents  what  acid ?  What  base,  or  hydrate?  Write 
the  equation  for  making  KI  from  its  acid  and  base.  Describe  the  ex- 
periment in  full.  Classify,  as  to  acids,  bases,  or  salts :  KBr,  Fe(OH)2, 
HI,  NaBr,  HNO2,  A12(OH)6,  KC1O3,  HC1O3,  H2S,  K2S,  H2SO3,  K2SO4, 
Ca(OH)2,  CaCO3,  NaBrO3,  CaSO4,  H2CO3,  K2CO3,  Cu(OH)2,  Cu(NO3)2, 
PbSO4,  H3PO4,  Na3PO4.  In  the  salts  above,  draw  a  light  vertical  line, 
separating  the  positive  from  the  negative  part  of  the  symbol.  Now 
state  what  acid  each  represents.  What  base.  Write  the  reaction 
in  the  preparation  of  each  salt  above  from  its  acid  and  base ;  then 
state  the  experiment  for  producing  it. 

74.  Naming-  Salts. —  (NO3)  is  the  nitrate  radical;  KNO3  is 
potassium  nitrate.     From  what  acid?     (NO2)  is  the  nitrite  radical; 
KNO2  is  potassium  nitrite.     From  what  acid?     Note  that  the  end- 
ings of  the  acids  are  ous  and  ic  ;  also  that  the  names  of  their  salts  end 
in  ite  and  ate.     From  which  acid  —  ic  or  ous  —  is  the  salt  ending  in 
ate  derived  ?     That  ending  in  ite  f 

Name  these  salts,  the  acids  from  which  they  are  derived,  and  the  end- 
ings of  both  acids  and  salts:  NaNO3,  NaNO2,.K2SO4,  K2SO3,  CaSO4, 
CaSO3,  KC1O3,  KC1O2,  KC1O,  KC1O4  (use  prefixes  Jiypo  and  per,  as  with 
acids),  Ca^PO,),,  Ca^PO,),,  CuSO4,  CuSO3,  AgNO3,  Cu(NO3)2.  FeS, 
FeS2,  are  respectively  ferrous  sulphide  and  ferric  sulphide.  Name  : 
HgCl,  HgCl2,  FeCl2,  Fe2Cl6,  FeSO4,  Fe2(SO4)3. 


SALTS.  55 

75.  Acid  Salts.  —  Write  symbols  for  nitric,  sulphuric,  phos- 
phoric acids.     How  many  H  atoms  in  each  ?     Replace  all  the  H  in  the 
symbol  of  each  with  Na,  and  name  the  products.     Again,  in  sulphuric 
acid  replace  one  atom  of  H  with  Na ;  then  in  phosphoric  replace  first 
one,  then  two,  and  finally  three  H  atoms  with  Na.    HNaSO4  is  hydrogen 
sodium  sulphate  ;   HNa2PO4  is  hydrogen  di-sodiurn  phosphate.     Name 
the   other   salts    symbolized.      Name  HNaNH4PO4.      Though   these 
products  are  all  salts,   some   contain  replaceable  H,  and  are  called 
acid  salts.      Those  which  have  all  the  H  replaced  by  a  metal  are 
normal  salts.     Name  and  classify,  as  to  normal  or  acid  salts  :  Na2CO3, 
HNaC03,  K2S04,  HKSO4,  (NH4)2SO4,  HNH4SO4,  Na3PO4,  HNa2PO4, 
H2NaPO4. 

The  basicity  of  an  acid  is  determined  by  the  number  of  replaceable 
H  atoms  in  its  molecule.  It  is  called  monobasic  if  it  lias  one ;  dibasic 
if  two ;  tri-  if  three,  etc.  Note  the  basicity  of  each  acid  named  above. 
How  many  possible  salts  of  H2SO4  with  Na?  Of  H3PO4  with  Na? 
Which  are  normal  and  which  acid  ?  What  is  the  basicity  of  H4SiO4  ? 

Some  normal,  as  well  as  acid,  salts  change  litmus.  Na.2CO3,  repre- 
senting a  strong  base  and  a  weak  acid,  turns  it  blue.  There  are  other 
modes  of  obtaining  salts,  but  this  is  the  only  one  which  we  shall  consider. 

76.  Salts  Occur  Abundantly  in  Nature,  such  as  NaCl, 
MgSO4,  CaCO3.    Acids  and  bases  are  found  in  small  quan- 
tities only.     Why  is  this?     Why  are    there  not  springs 
of  H2SO4  and  NH4OH?     We  have  seen  that  acids  and 
bases  are  extremely  active,  have  opposite  characters,  and 
combine  to  form  relatively  inactive  salts.     If  they  existed 
in   the   free  state,  they  would  soon  combine  by  reason 
of  their  strong  affinities.     This  is  what  in  all  ages  of  the 
world  has  taken   place,  and   this  is  why  salts   are    com- 
mon, acids  and  bases  rare.     Active  agents   rarely  exist 
in  the  free  state  in  large  quantities.      Oxygen  seems  to 
be  an  exception,  but  this  is  because  there  is  a  superabun- 
dance of  it.      While  vast  quantities  are  locked  up  in  com- 
pounds  in   rocks,  water,    and   salts   of  the   earth,  much 
remains  with  which  there  is  nothing  to  combine. 


CHAPTER   XVII. 


CHLORIIYDRIC  ACID. 


77.  We  have  seen  that  salts  are  made  by  the  union  of 
acids  and  bases.     Can  these  last  be  obtained  from  salts? 

78.  Preparation  of  HC1. 

Experiment  47.  —  Into  a  flask  put  10&  coarse  NaCl,  and  add  20CC 
H2SO4.  Connect  with  Woulff  bottles l 
partly  filled  with  water,  as  in  Figure  22. 
One  bottle  is  enough  to  collect  the  HC1 ; 
but  in  that  case  it  is  less  pure,  since 
some  H2SO4  and  other  impurities  are 
carried  over.  Several  may  be  connected, 
as  in  Figure  23.  The  water  in  the  first 
bottle  must  be  nearly  saturated  before 
much  gas  will  pass  into  the  second. 
Heat  the  mixture  15  or  20  minutes,  not 
very  strongly,  to  prevent  too  much  foam- 
ing. Notice  any  current  in,  the  first 
bottle.  NaCl  +  H2SO4=  HNaSO4+HCl. 
Intense  heat  would  have  given :  2  NaCl 
+  H2SO4  =  Na.2SO4  +  2  HC1.  Compare 
these  equations  with  those  for  HNO3. 
In  which  equation  above  is  H2SO4  used 

most  economically?    Both  reactions  take  place  when  HC1  is  made  on 

the  large  scale. 

79.  Tests. 

Experiment  48.  —  (1)  Test  with  litmus  the  liquid  in  each  Woulff 

1  Woulff  bottles  may  be  made  by  fitting  to  wide-mouthed  bottles  corks  with  three 
holes,  through  which  pass  two  delivery  tubes,and  a  central  safety  tube  dipping  into  the 
liquid,  as  in  Figures  22  and  23. 


Fig. 


CHLORHYDRIC   ACID.  57 

bottle.  (2)  Put  a  piece  of  Zn  into  a  t.t.  and  cover  it  with  liquid  from 
the  first  bottle.  Write  the  reaction,  arid  test  the  gas.  (3)  To  2CC  solu- 
tion AgNO3  (page  208)  in  a  t.t,  add  2CC  of  the  acid.  Describe,  and 
write  the  reaction.  Is  AgCl  soluble  in  water?  (4)  Into  a  t.t.  pour 
5CC  Pb(NO3)2  solution,  and  add  the  same  amount  of  prepared  acid. 
Give  the  description  and  the  re- 
action. (5)  In  the  same  way  test 
the  acid  with  Hg2(NO3)2  solu- 
tion, giving  the  reaction.  (6) 
Make  a  little  HC1  in  a  t.t.,  and 
bring  the  gas  escaping  from  the 
d.t.  in  contact  with  a  burning 
stick.  Does  it  support  the  com- 
bustion of  C  ?  (7)  Hold  a  piece  Fig  «j3< 
of  dry  litmus  paper  against  it. 

(8)  Hold  it  over  2CC  of  NH4OH  in  an  evaporating-dish.  Describe, 
name  the  product,  and  write  the  reaction.  (3),  (4),  (5),  (8),  are 
characteristic  tests  for  this  acid. 

8O.  Chlorhydric,  Hydrochloric  or  Muriatic,  Acid  is 
a  Gas.  —  As  used,  it  is  dissolved  in  water,  for  which  it  has 
great  affinity.  Water  will  hold,  according  to  temperature, 
from  400  to  500  times  its  volume  of  HC1.  Hundreds  of 
thousands  of  tons  of  the  acid  are  annually  made,  mostly  in 
Europe,  as  a  bye-product  in  Na2CO3  manufacture.  The  gas 
is  passed  into  towers  through  which  a  spray  of  water  falls ; 
this  absorbs  it.  The  yellow  color  in  most  commercial  HC1 
indicates  impurities,  some  of  which,  are  Fe,  S,  As,  and  or- 
ganic matter.  As,  S,  etc.,  come  from  the  pyrites  used  in 
making  H2SO4.  Chemically  pure  (C.P.)  acid  is  freed  from 
these,  and  is  without  color.  The  gas  may  be  dried  by 
passing  it  through  a  glass  tube  holding  CaCl2  (Fig.  16) 
and  collecting  it  over  mercury. 

The  muriatic  acid  of  commerce  consists  of  about  two- 
thirds  water  by  weight.  HC1  can  also  be  made  by  direct 
union  of  its  constituents  (page  100). 


58  FLUORHYDRIC   ACID. 

81.  Uses.  —  HC1  is  used  to  make  Cl,  and  also  bleaching- 
powder.     Its  use  as  a  reagent  in  the  laboratory  is  illus- 
trated by  the  following  experiment:  — 

Experiment  49.  — Put  into  a  t.t.  2CC  AgNO3  solution,  add  5CC 
H2O,  then  add  slowly  HC1  so  long  as  a  ppt.  (precipitate)  is  formed. 
This  ppt.  is  AgCl.  Now  in  another  t.t.  put  2CC  Cu(NO3),  solu- 
tion, add  5CC  H2O,  then  a  little  HC1.  No  ppt.  is  formed.  Now  if  a 
solution  of  AgNO3  and  a  solution  of  Cu(NO3)2  were  mixed,  and  HC1 
added,  it  is  evident  that  the  silver  would  be  precipitated  as  chloride  of 
silver,  while  the  copper  would  remain  in  solution.  If  now  this  be  fil- 
tered, the  silver  will  remain  on  the  filter  paper,  while  in  the  filtrate  will 
be  the  copper.  Thus  we  shall  have  performed  an  analysis,  or  sepa- 
rated one  metal  from  another.  Perform  it.  Note,  however,  that 
any  soluble  chloride,  as  NaCl,  would  produce  the  same  result  as 
HC1. 

BROMHYDRIC    AND   IODIHYDRIC    ACIDS. 

82.  NaCl,  being  the  most  abundant  compound  of  Cl,  is 
the  source  of  commercial  HC1.     KC1  treated  in  the  same 
way  would  give  a  like  product.     Theoretically  HBr  and 
HI  might  be  made  in  the  same  way  from  NaBr  and  Nal, 
but  the  affinity  of  H  for  Br  and  I  is  weak,  and  the  acids 
separate  into  their  elements,  when  thus  prepared. 

83.  To  make  HI. 

Experiment  50.  —  Drop  into  a  t.t.  three  or  four  crystals  of  I,  and 
add  10CC  H2O.  Hold  in  the  water  the  end  of  a  d.t.  from  which  H2S 
gas  is  escaping  (page  120).  Observe  any  deposit,  and  write  the 
reaction. 

FLUORHYDRIC    ACID. 

84.  Preparation  and  Action. 

Experiment  51.  —  Put  3  or  4s  powdered  CaF2,  i.e.  fluor  sparer  fluo- 
rite,  into  a  shallow  lead  tray,  e.g.  4  X  5cm,  and  pour  over  it  4  or  5CC  H2SO4. 
A  piece  of  glass  large  enough  to  cover  this  should  previously  be  warmed 
and  covered  on  one  side  with  a  very  thin  coat  of  beeswax.  To  distribute  it 


FLUORHYDRIC   ACID.  59 

evenly,  warm  the  other  side  of  the  glass  over  a  flame.  When  cool,  scratch 
a  design  (Fig.  24)  through  the  wax  with  a  sharp  metallic  point.  Lay  the 
glass,  film  side  down,  over  the  lead  tray.  Warm  this  five  minutes  or  more 

by  placing  it  high   over    a 

— >^  )        \   small  flame  (Fig.  25)  to  avoid 
^f         \  melting  the  wax.    Do  not  in- 
hale the  fumes.     Take  away 
Fig.  24.  the  lamp,  and  leave  the  tray 

and  glass  where  it  is  not  cold,  for  half  an  hour  or 
more.  Then  remove  the  wax  and  clean  the  glass 
with  naphtha  or  benzine.  Look  for  the  etching. 

Two  things  should  have  occurred  :  (1) 
the  generation  of  HF.  Write  the  equation 
for  it.  (2)  Its  etching  action  on  glass.  Fig.  25. 

In  this  last  process  HF  acts  on  SiO2  of  the  glass,  form- 
ing H2O  and  SiF4.  Why  cannot  HF  be  kept  in  glass 
bottles  ? 

A  dilute  solution  of  HF,  which  is  a  gas,  may  be  kept  in  gutta  percha 
bottles,  the  anhydrous  acid  in  platinum  only ;  but  for  the  most  part,  it  is 
used  as  soon  as  made,  its  chief  use  being  to  etch  designs  on  glass-ware. 
Glass  is  also  often  etched  by  a  blast  of  sand  (SiO2). 

Notice  the  absence  of  O  in  the  acids  HF,  HC1,  HBr,  HI,  and  that  each 
is  a  gas.  HF  is  the  onljr  acid  that  will  dissolve  or  act  appreciably  on 
glass. 


CHAPTER   XVIII. 


NITRIC  ACID. 


85.    Preparation. 


Experiment  52.  — To  108  KNO3  or  NaNO3,  in  a  flask,  add  15CC 
H2SO4.  Securely  fasten  the  cork  of  the  d.t.,  as  HNO3  is  likely  to  loosen 
it,  and  pass  the  other  end  to  the  bottom  of  a  t.t.  held  deep  in  a  bottle  of 
water  (Fig.  26).  Apply  heat,  and  collect  4  or  5CC  of  the  liquid.  Th< 


Fig.  26. 


Fig.  27. 


usual  reaction  is:  KNO3  +  H2SO4=HKSO4+HNO3.  With  greater 
heat,  2  KNO3  +  H2SO4  =  K2SO4  +  2  HNO3.  Which  is  most  economical 
of  KNO3?  Of  H2SO4?  Instead  of  a  flask,  a  t.t.  may  be  used  if  de- 
sired (Fig.  27). 

86.    Properties  and  Tests. 

Experiment  53. —  (1)  Note  the  color  of  the  prepared  liquid.    (2) 
Put  a  4rop  on  the  finger;  then  wash  it  off  at  once,    (3)  Pip  a  quill 


NITRIC   ACID.  61 

or  piece  of  white  silk  into  it ;  then  wash  off  the  acid.  What  color 
is  imparted  to  animal  substances  ?  (4)  Add  a  little  to  a  few  bits  of 
Cu  turnings,  or  to  a  Cu  coin.  WTrite  the  equation  (page  42).  (5) 
To  2CC  indigo  solution  add  2CC  HNO3.  State  the  leading  properties 
of  HNO3  from  these  tests. 

87.  Chemically  Pure  HNO3  is  a  Colorless  Liquid. — 

The  yellow  color  of  that  prepared  in  Experiment  52  is 
due  to  liquid  NO2  dissolved  in  it.  It  is  then  called 
fuming  HNO3,  and  is  very  strong.  NO2  is  formed  at  a  high 
temperature. 

Commercial  or  ordinary  HNO3is  made  from  NaNO3,  this 
being  cheaper  than  KNO3 ;  it  is  about  half  water. 

88.  Uses.  —  HNO3  is  the    basis   of   many  nitrates,    as 
AgNO3,  used  for  photography,  Ba(NO3)2and  Sr(NO3)2for 
fire-works,  and  others  for  dyeing  and  printing  calico;    it  is 
employed  in  making  aqua  regia,  sulphuric  acid,  nitro-gly- 
cerine,  gun-cotton,  aniline  colors,  zylonite,  etc. 

Enough  experiments  have  been  performed  to  answer  the 
question  whether  some  acids  can  be  prepared  from  their 
salts.  H2SO4  is  not  so  made,  because  no  acid  is  strong 
enough  to  act  on  its  salts.  In  making  HC1,  HNO3,  etc., 
sulphuric  acid  was  used,  being  the  strongest. 

AQUA   REGIA. 

89.  Preparation  and  Action. 

Experiment  54.  —  Into  a  t.t.  put  2CC  HNO3  and  l^cra  of  either  Au 
leaf  or  Pt.  Warm  in  a  flame.  If  the  metal  is  pure,  no  action  takes 
place.  Into  another  tube  put  6CC  HC1  and  add  a  similar  leaf.  Heat 
this  also.  There  should  be  no  action.  Pour  the  contents  of  one  t.t. 
into  the  other.  Note  the  effect.  Which  is  stronger,  one  of  the  acids, 
or  the  combination  of  the  two?  Note  the  odor.  It  is  that  of  Cl. 
3  HC1  +  HNO3  =  NOC1  +  2  H2O  +  C12.  This  reaction  is  approximate 
only.  The  strength  is  owing  to  nascent  chlorine,  which  unites  with 
Au.  Au  +  3  CJ ~  AuCl§.  If  Pt  be  used,  PtCl*  is  produced, 


62  ,    NITRIC    ACID. 

No  other  acid  except  mtro-hydrochloric  will  dissolve 
Au  or  Pt ;  hence  the  ancients  called  it  aqua  regia,  or  king 
of  liquids.  It  must  be  made  as  wanted,  since  it  cannot 
be  kept  and  retain  its  strength. 


CHAPTER    XIX. 

SULPHURIC  ACID. 

OO.    Preparation. 

Experiment  55.  —  Having  fitted  a  cork  with  four  or  five  perfora- 
tions to  a  large  t.t.,  pass  a  d.t.  from  three  of  these  to  three  smaller  t.t., 
leaving  the  others  open  to  the  air,  as 
in  Figure  28.  Into  one  t.t.  put  5CC 
II2O,  into  another  5s  Cu  turnings  and 
10CC  H2SO4,  into  the  third  5*  Cu  turn- 
ings and  lO00  dilute  HNO3,  half  wa- 
ter. Hang  on  a  ring  stand,  and  slowly 
heat  the  tubes  containing  H2O  and 
H.,SO4.  Notice  the  fumes  that  pass 
into  the  large  t.t. 

Trace  out  and  apply  to  Fig- 
ure 28  these  reactions  :  — 

(1)  Cu  +  2H2S04  =  CuS04  + 
2H20  +  SO2. 

(2)  3  Cu  +  8  HNO3  =  3  Cu  (NO3)2  +  4  H0O  +  2  NO. 

(3)  NO+O=N02. 

(4)  S02+H20+N02  =  H2SO4  +  NO. 

(4)  comes  from  combining  the  gaseous  products  in  (1), 
(2),  (3).  In  (3),  NO  takes  an  atom  of  O  from  the  air, 
becoming  NO2,  and  at  once  gives  it  up  to  the  H2SO3 
(H2O  +  SO2),  making  H2SO4,  and  again  goes  through  the 
same  operation  of  taking  up  O  and  passing  it  along.  NO 
is  thus  called  a  carrier  of  O.  It  is  a  reducing  agent,  while 
NO2  is  an  oxidizing  agent.  This  is  a  continuous  process, 


64  SULPHURIC    ACID. 

and  very  important,  since  it  changes  useless  •  H2SO3  into 
valuable  H2SO4.  If  exposed  to  the  air,  H2SO3  would  very 
slowly  take  up  O  and  become  H2SO4. 

Instead  of  the  last  experiment,  this  may*  be  employed  if  preferred : 
Burn  a  little  S  in  a  receiver.  Put  into  an  evaporating-dish,  5CC  HNO3,  and 
dip  a  paper  or  piece  of  cloth  into  it.  Hang  the  paper  in  the  receiver  of 
SO2,  letting  no  HNO3  drop  from  it.  Continue  this  operation  till  a  small 
quantity  of  liquid  is  found  in  the  bottle.  The  fumes  show  that  HN03  has 
lost  O.  2  HNO3  +  S02  =  H,S04  +  2  N02. 

91.  Tests  for  H,SO4. 

Experiment  56. —  (1)  Test  the  liquid  with  litmus.  (2)  Transfer  it 
to  a  t.t. ,  and  add  an  equal  volume  of  13aCl2  solution.  H2SO4  +  BaCl2  =  ? 
Is  BaSO4  soluble?  (3)  Put  one  drop  H2SO4  from  the  reagent  bottle  in 
10CC  H2O  in  a  clean  t.t.,  and  add  lcc  BaCl2  solution.  Look  for  any  cloudi- 
ness. This  is  the  characteristic  test  for  II2SO4  and  soluble  sulphates, 
and  so  delicate  that  one  drop  in  a  liter  of  H2O  can  be  detected.  (4) 
Instead  of  H2SO4,  try  a  little  Na2SO4  solution.  (5)  Put  two  or  three 
drops  of  strong  H2SO4  on  writing-paper,  and  evaporate,  high  over  a 
flame,  so  as  not  to  burn  the  paper.  Examine  it  when  dry.  (6)  Put  a  stick 
into  a  t.t.  containing  2CC  H2SO4,  and  note  the  effect.  (7)  Review  Experi- 
ment 5.  (8)  Into  an  e.d.  pour  5CC  H2O,  and  then  15CC  H2SO4.  Stir  it 
meantime  with  a  small  t.t.  containing  2  or  3CC  NH4OH,  and  notice 
what  takes  place  in  the  latter ;  also  note  the  heat  of  the  e.d. 

The  effects  of  (5),  (6),  (7),  and  (8)  are  due  to  the  intense  affinity 
which  H2SO4  has  for  H2O.  So  thirsty  is  it  that  it  even  abstracts  H 
and  O  from  oxalic  acid  in  the  right  proportion  to  form  H2O,  combines 
them,  and  then  absorbs  the  water. 

92.  Affinity  for  Water.  —  This   acid   is  a   desiccator 
or  dryer,  and  is  used  to  take  moisture  from  the  air  and 
prevent  metallic  substances  from  rusting.     In  this  way  it 
dilutes  itself,  and  may  increase  its  weight  threefold.     In 
diluting,  the  acid  must  always  be  poured  into  the  water 
slowly  and  with  stirring,  not  water  into  the  acid,  since,  as 
H2O  is  lighter  than  H2SO4,  heat  enough  may  be  set  free  at 
the  surface  of  contact  to  cause  an  explosion, 


SULPHURIC    ACID. 


65 


Contraction  also  takes  place,  as  may  be  shown  by  accu- 
rately measuring  each  liquid  in  a  graduate,  before  mixing, 
and  again  when  cold.  The  mixture  occupies  less  volume 
than  the  sum  of  the  two  volumes.  For  the  best  results 
the  volume  of  the  acid  should  be  about  three  times  that  of 
the  water. 

93.  Sulphuric  Acid  made  on  a  Large  Scale  involves 
the  same  principles  as  shown  in  Experiment  55,  excepting 
that  SO2is  obtained  by  burning  S  or  roasting  FeS2  (pyrite), 


Fig.  29. 

and  HNO3  is  made  on  the  spot  from  NaNO3  and  H2SO4o 
SO2  enters  a  large  leaden  chamber,  often  100  to  300  feet 
long,  and  jets  of  steam  and  small  portions  of  HNO3  are 
also  forced  in.  The  "chamber  acid"  thus  formed  is  very 
dilute,  and  must  be  evaporated  first  in  leaden  pans,  and 
finally  in  glass  or  platinum  retorts,  since  strong  H2SO4, 
especially  if  hot,  dissolves  lead.  See  Experiment  124. 
Study  Figure  29,  and  write  the  reactions.  2  HNO8  breaks 
up  into  2  NO2,  5,O,  and  O. 


66  SULPHURIC   ACID. 

94.  Importance.  —  Sulphuric  acid  has  been  called,  next 
to  human  food,  the  most  indispensable  article  known.  There 
is  hardly  a  product  of  modern  civilization  in  the  manufac- 
ture of  which  it  is  not  directly  or  indirectly  used.     Nearly 
a   million  tons  are  made  yearly  in  Great  Britain  alone. 
It  is  the  basis  of  all  acids,  as  Na2CO3  is  of  alkalies.     It  is 
the  life  of  chemical  industry,  and  the  quantity  of  it  con- 
sumed is  an  index  of  a  people's  civilization.    Only  a  few  of 
its  uses  can  be  stated  here.     The  two  leading  ones  are  the 
reduction  of  Ca3(PO4)2  for  artificial  manures  (see  page  123) 
and  the  sodium  carbonate  manufacture.      Foods  depend 
on  the  productiveness  of  soils  and  on  fertilizers,  and  thus 
indirectly  our  daily  bread  is  supplied  by  means  of  this  acid ; 
and  from  sodium  carbonate  glass,  soap,  saleratus,  baking- 
powders,  and  most  alkalies  are  made  directly  or  indirectly. 
H2SO4  is  employed  in  bleaching,  dyeing,  printing,  telegra- 
phy, electroplating,  galvanizing   iron   and  wire,  cleaning 
metals,  refining  Au  and  Ag,  making  alum,  blacking,  vit- 
riols., glucose,  mineral  waters,  ether,  indigo,  madder,  nitro- 
glycerine, gun-cotton,  parchment,  celluloid,  etc.,  etc. 

FUMING  SULPHURIC   ACID. 

95.  Nordhausen  or  Fuming  Sulphuric  Acid,  H2S2O7,  used 
in  dissolving  indigo  and  preparing  coal-tar  pigments,  is  made  by  distilling 
FeSO4.    4  FeSO4  +  H2O  =  H2S2O7  +  2  Fe203  +  2  SO2.     This  was  the  original 
sulphuric  acid.     It  is  also  formed  when  S03  is  dissolved  in  H2S04.     When 
exposed  to  the  air,  S03  escapes  with  fuming. 


CHAPTER   XX. 

AMMONIUM  HYDRATE. 

96.  Preparation  of  Bases.  —  We  have  seen  that  many 
acids  are  made  by  acting  on  a  salt  of  the  acid  required,  with 
a  stronger  acid.     This  is  the  direct  way.     The  following 
experiments  will  show  that  bases  may  be  prepared  in  a 
similar  way  by  acting  on  salts  of  the  base  required  with 
other  bases,  which  we  may  regard  as  stronger  than  the  ones 
to  be  obtained. 

97.  Preparation  of  NH4OH  and  NH3. 

Experiment  57.  —  Powder  10g  ammonium  chloride,  NH4C1,  in  a 
mortar  and  mix  with  10s  calcium  hydrate,  Ca(OH)2 ;  recently  slaked 
lime  is  the  best.  Cover  with  water  in  a  flask,  and  connect  with 
Woulff  bottles,  as  for  making  I1C1  (Fig.  22)  ;  heat  the  flask  for  fifteen 
minutes  or  more.  The  experiment  may  be  tried  on  a  smaller  scale 
with  a  t.t.  if  desired. 

The  reaction  is :  2  NH4C1  +  Ca(OH)2  =  CaCl2+  2  NH4OH. 
NH4OH  is  broken  up  into  NH3,  ammonia  gas,  and 
water.  NH4OH  =  NH3  +  H2O.  These  -pass  over  into  the 
first  bottle,  where  the  water  takes  up  the  NH;J,  for  which 
it  has  great  affinit}^.  One  volume  of  water  at  0°  will  absorb 
more  than  1000  volumes  of  NHS,  Thus  NH4OH  may  be 
called  a  solution  of  NH3  in  H2O.  Write  the  reaction. 

Experiment  58. —  Powder  and  mix  2  or  38  each  of  ammonium 
nitrate,  NH4NO3,  and  Ca(OH)2 ;  put  them  into  a  t.t.,  and  heat  slowly. 
Note  the  odor.  2  NH4NO3  +  Ca(OH)2  =  ? 

98.  Tests. 

Experiment  59.  —  (1)  Generate  a  little  of  the  gas  in  a  t.t.,  and 
note  the  odor.  (2)  Test  the  gas  with  wet  red  litmus  paper.  (3)  Put 


68  AMMONIUM   HYDRATE. 

a  little  HC1  into  an  e.d.,  and  pass  over  it  the  fumes  of  NH3  from 
a  d.t.  Note  the  result,  and  write  the  equation.  (4)  Fill  a  small 
t.t.  with  the  gas  by  upward  displacement ;  then,  while  still  inverted, 
put  the  mouth  of  the  t.t.  into  water.  Explain  the  rise  of  the  water. 
(5)  How  might  JSTH4C1  be  obtained  from  the  NH4OH  in  the  Woulff 
bottles  ?  (6)  Test  the  liquid  in  each  bottle  with  red  litmus  paper.  (7) 
Add  some  from  the  first  bottle  to  5  or  10CC  of  a  solution  of.  FeSO4  or 
FeCl2,  and  look  for  a  ppt.  State  the  reaction. 

99.  Formation.  —  Ammonia,  hartshorn,  exists  in  animal 
and  vegetable  compounds,  in  salts,  and,  in  small  quantities, 
in  the  atmosphere.     Rain  washes  it  from  the  atmosphere 
into  the  soil ;  plants  take  it  from  the  soil ;  animals  extract 
it   from  plants.      Coal,  bones,  horns,  etc.,  are  the  chief 
sources  of  it,  and  from  them  it  is  obtained  by  distillation. 
It  results  also  from  decomposing  animal  matter.     NH3  can 
be  produced  by  the  direct  union  of  N  and  H,  only  by  an 
electric  discharge  or  by  ozone  (see  page  85).     It  may  be 
collected  over  Hg  like  other  gases  tbat  are  very  soluble  in 
water. 

100.  Uses.  —  Ammonium  hydrate,  NH4OH,  and  ammo- 
nia, NH3,  are  used  in  chemical  operations,  in  making  artifi- 
cial ice,  and  to  some  extent  in  medicine;  from  them  also 
may  be  obtained  ammonium  salts.     State  what  you  would 
put    with    NH4OH    to    obtain    (NH4)2SO4.      To    obtain 
NH4  NO3.     The  use  of  NH4OH  in  the  laboratory  may  be 
illustrated  by  the  following  experiment :  — 

Experiment  60.  —  Into  a  t.t.  put  10CC  of  a  solution  of  ferrous  sul- 
phate, FeSO4.  Into  another  put  10CC  of  sodium  sulphate  solution, 
Na2SO4.  Add  a  little  NH4OH  to  each.  Notice  a  ppt.  in  the  one  case 
but  none  in  the  other.  If  solutions  of  these  two  compounds  were  mixed, 
the  metals  Fe  and  Na  could  be  separated  by  the  addition  of  NH4OH, 
similar  to  the  separation  of  Ag  and  Cu  by  HC1.  See  page  58.  Try  the 
experiment. 


CHAPTER   XXL 

SODIUM  HYDRATE. 

1O1.    Preparation. 

Experiment  61.  —  Dissolve  3s  sodium  carbonate,  Na2CO3,  in  10  or 
15CC  H2O  in  an  e.d.,  and  bring  it  to  the  boiling-point.  Then  add  to 
this  a  mixture  of  1  or  2^  calcium  hydrate,  Ca(OH)2,  in  5  or  10CC  H2O. 
It  will  not  dissolve.  Boil  the  whole  for  five  minutes.  Then  pour 
off  the  liquid  which  holds  NaOH  in  solution.  Evaporate  if  desired. 
This  is  the  usual  mode  of  preparing  NaOH. 

The  reaction  is  Na2CO3  +  Ca(OH)2  -  2  NaOH  +  CaCO3. 
The  residue  is  Ca(OH)2  and  CaCO3;  the  solution  con- 
tains NaOH,  which  can  be  solidified  by  evaporating  the 
water.  Sodium  hydrate  is  an  ingredient  in  the  manu- 
facture of  hard  soap,  and  for  this  use  thousands  of 
tons  are  made  annually,  mostly  in  Europe.  It  is  an 
important  laboratory  reagent,  its  use  being  similar  to  that 
of  ammonium  hydrate.  Exposed  to  the  air,  it  takes  up 
water  and  CO2,  forming  a  mixture  of  NaOH  and  Na2CO3. 
It  is  one  of  the  strongest  alkalies,  and  corrodes  the  skin. 

Experiment  62.  —  Put  20CC  of  H2O  in  a  receiver.  With  the  forceps 
take  a  piece  of  Na,  not  larger  than  half  a  pea,  from  the  naphtha  in 
which  it  is  kept,  drop  it  into  the  H2O,  and  at  once  cover  .the  receiver 
loosely  with  paper  or  cardboard.  Watch  the  action,  as  the  Na  decom- 
poses H2O.  HOH  +  Na  =  NaOH  +  H.  If  the  water  be  hot  the  action  is 
so  rapid  that  enough  heat  is  produced  to  set  the  H  on  fire.  That  the  gas 
is  H  can  be  shown  by  putting  the  Na  under  the  mouth  of  a  small  in- 
verted t.t.,  filled  with  cold  water,  in  a  water-pan.  Na  rises  to  the  top, 
and  the  t.t.  fills  with  H,  which  can  be  tested.  NaOH  dissolves  in  the 
water. 


70  CALCIUM   HYDRATE. 

102.  Properties. 

Experiment  63.  —  (1)  Test  with  red  litmus  paper  the  solutions 
obtained  in  the  last  two  experiments.  (2)  To  5CC  of  alum  solution, 
K2A12(SO4)4,  add  2CC  of  the  liquid,  and  notice  the  color  and  form  of 
the  ppt. 

POTASSIUM   HYDRATE. 

103.  KOH  is  made  in  the  Same  Way  as  NaOH.— 

Describe  the  process  in  full  (Experiment  61),  and  give  the 
equation. 

Experiment  64.  —  Drop  a  small  piece  of  K  into  a  receiver  of  H2O, 
as  in  Experiment  62.  The  K  must  be  very  small,  and  the  experiment 
should  not  be  watched  at  too  close  a  range.  The  receiver  should  not 
be  covered  with  glass,  but  with  paper.  The  H  burns,  uniting  with  O 
of  the  air.  The  purple  color  is  imparted  by  the  burning,  or  oxida- 
tion of  small  particles  of  K.  Write  the  equation  for  the  combustion 
of  each. 

H2O  might  be  considered  the  symbol  of  an  acid,  since  it  is  the  union  of 
H  and  a  negative  element ;  or,  if  written  HOH,  it  might  be  called  a  base, 
since  it  has  a  positive  element  and  the  (OH)  radical.  It  is  neutral  to  lit- 
mus, and  on  this  account  might  be  called  a  salt.  It  is  better,  however,  to 
call  it  simply  an  oxide. 

Potassium  hydrate,  caustic  potash,  is  employed  for  the 
manufacture  of  soft  soap.  See  page  187.  As  a  chemical 
reagent  its  action  is  almost  precisely  like  that  of  caustic 
soda,  though  it  is  usually  considered  a  stronger  base,  as 
K  is  a  more  electro-positive  element  than  Na. 

CALCIUM   HYDRATE. 

104.  Calcium    Hydrate,    the    Most    Common  of   the 

Bases,  is  nearly  as  important  to  them  as  H2SO4  is  to 
acids.  Since  it  is  used  to  make  the  other  bases,  it  might 
be  called  the  strongest  base,  as  H2SO4  is  often  called  the 
strongest  acid.  The  strength  of  an  acid  or  base,  however, 


HYDRATES.  71 

depends  on  the  substance  to  which  it  is  applied,  as  well  as 
on  itself,  and  for  most  purposes  this  one  is  classified  as  a 
weaker  base  than  the  three  previously  described. 

Sulphuric  acid,  the  most  useful  of  the  acids,  is  not  made 
directly  from  its  salts,  but  has  to  be  synthesized.  Calcium 
hydrate  is  also  made  by  an. indirect  process,  as  follows  : 

CaCO3,  i.e.  limestone,  marble,  etc.,  is  burnt  in  kilns  with 
C,  a  process  which  separates  the  gas,  CO2,  according  to  the 
reaction:  CaCO3  =  CaO  +  CO2.  CaO  is  unslaked  lime,  or 
quick-lime.  On  treating  this  with  water,  slaked  lime, 
Ca(OH)2  is  formed,  with  generation  of  great  heat.  CaO 
+  H2O  -  Ca(OH)2.  Its  affinity  for  H2O  is  so  great  that 
it  takes  the  latter  from  the  air,  if  exposed. 

Experiment  65.  —  Saturate  some  unslaked  lime  with  water,  in 
an  e.d.,  and  look  for  the  results  stated  above,  leaving  it  as  long  as 
may  be  necessary. 

1O5.  R£sum6.  —  From  the  experiments  in  the  last  few 
chapters  on  the  three  divisions  of  chemical  compounds, 
acids,  bases  and  salts,  we  have  seen  (1)  that  acids  and 
bases  are  the  chemical  opposites  of  each  other ;  (2)  that 
salts  are  formed  by  the  union  of  acids  and  bases ;  (3) 
that  some  acids  can  be  obtained  from  their  salts  by  the 
action  of  a  stronger  acid ;  (4)  that  some  bases  can  be  got 
from  salts  by  the  similar  action  of  other  bases ;  (5)  that 
the  strongest  acids  and  bases,  as  well  as  others,  may  be 
obtained  in  an  indirect  way  by  synthesis. 


CHAPTER   XXII. 


OXIDES   OF  NJTROGEN. 

1O6.    There  are  five  oxides  of  N,  only  two  of  which 
are  important. 

NITROGEN  MONOXIDE    (N2O). 
1C  7.    Preparation. 

Experiment  66.  —  Put  into  a  flask,  holding  200CC ,  10&  of  ammonium 
nitrate,  NH4NO3;  heat  it  over  wire  gauze  or  asbestus  in  an  iron  plate, 

having  a  d.t.  connected 
with  a  large  t.t.,  which 
is  held  in  a  receiver  of 
water,  and  from  this 
t.t.,  another  d.t.  pass- 
ing into  a  pneumatic 
trough,  so  as  to  collect 
the  gas  over  water 
(Fig.  30).  Have  all  the 
bearings  tight.  The 
reaction  is  NH4NO3  = 
2H2O  +  N2O.  The  t.t.  is 
for  collecting  the  H2O. 


Fig.  30. 


Note  the  color  of  the 
liquid  in  the  t.t. ;  taste 
a  drop,  and  test  it  with  litmus.  If  the  flask  is  heated  too  fast,  some 
NO  is  formed,  and  this  taking  O  from  the  air  makes  NO2,  which 
liquefies  and  gives  an  acid  reaction  and  a  red  color.  Some  NH4NO3 
is  also  liable  to  be  carried  over. 

1O8.    Properties. 

Experiment  67.  —  Test  the  gas  in  the  receiver  with  a  burning  stick 
and  a  glowing  one,  and  compare  the  combustion  with  that  in  O.     N2O 


OXIDES   OF    NITROGEN.  73 

may  also  be  tested  with  S  and  P,  if  desired.      N  is  set  free  in  each 
case.     Write  the  reactions. 

Nitrogen  monoxide  or  protoxide,  the  nitrous  oxide  of 
dentists,  when  inhaled,  produces  insensibility  to  pain,  — 
anaesthesia,  —  and,  if  continued,  death  from  suffocation. 
Birds  die  in  half  a  minute  from  breathing  it.  Mixed  with 
one-fourth  O,  and  inhaled  for  a  minute  or  two,  it  pro- 
duces intoxication  and  laughter,  and  hence  is  called 
laughing  gas.  As  made  in  Experiment  66,  it  contains  Cl 
and  NO,  as  impurities,  and  should  not  be  breathed. 

NITROGEN   DIOXIDE    (NO,    OR    N2O2). 

109.  Preparation. 

Experiment  68.  —  Into  a  t.t.  or  receiver  put  5s  Cu  turnings,  add 
5CC  H2O  and  5™  HNO3.  Collect  the  gas  like  H,  over  water.  3  Cu  + 
8  HNO3=:?  What  two  products  will  be  left  in  the  generator?  Notice 
the  color  of  the  liquid.  This  color  is  characteristic  of  Cu  salts. 
Notice  also  the  red  fumes  of  NO2. 

1 1 0.  Properties . 

Experiment  69.  —  Test  the  gas  with  a  burning  stick,  admitting 
as  little  air  as  possible.  Test  it  with  burning  S.  NO  is  not  a  supporter 
of  C  and  S  combustion.  Put  a  small  bit  of  P  in  a  deflagrating- 
spoon,  and  when  it  is  vigorously  burning,  lower  it  into  the  gas.  It 
should  continue  to  burn.  State  the  reaction.  What  combustion  will 
NO  support?  Note  that  NO  is  half  N,  while  N2O  is  two-thirds  N, 
and  account  for  the  difference  in  supporting  combustion. 

NITROGEN   TETROXIDE    (NO2  Or  N2O4). 

111.  Preparation. 

Experiment  70. —  Lift  from  the  water-pan  a  receiver  of  NO,  and 
note  the  colored  fumes.  They  are  NO2,  or  N2O4,  nitrogen  tetroxide. 
NO  +  O  =  NO2.  Is  NO  combustible?  What  is  the  source  of  O  in  the 
experiment? 


74  OXIDES   OF  NITROGEN. 

NITROGEN   TRIOXIDE  (N2O3). 
112.    Preparation. 

Experiment  71.  —  Put  into  a  t.t.  1&  of  starch  and  lcc  of  HNO3. 
Heat  the  mixture  for  a  minute.  The  red  fumes  are  N2O3  and  NO2. 

Nitrogen  pentoxide,  N2O5,  is  an  unimportant  solid.  United  with 
water  it  forms  HNO3.  N2O5  +  H2O  =  2  HNO3. 


CHAPTER   XXIII. 

LAWS    OF  DEFINITE    AND    OF   MULTIPLE    PRO- 
PORTION. 

113.  Weight  and  Volume.  —  We  have  seen  that  water 
contains  two  parts  of  H  by  volume  to  one  part  of  O  ;  or,  by 
weight,  two  parts  of  H  to  sixteen  of  O.     These  proportions 
are  invariable,  or  no  symbol  for  water  would  be  possible. 
Every  compound  in  the  same  way  has  an  unvarying  pro- 
portion of  elements. 

114.  Law  of  Definite  Proportion.  —  In  a  given  com- 
pound the  proportion  of  any  element  by  weight,  or,  if  a  gas, 
by  volume  is  always  constant.     Apply  the  law,  by  weight 
and  by  volume,  to  these :  HC1,  NH3,  H2S,  N2O. 

There  is  another  law  of  equal  importance  in  chemistry, 
which  the  compounds  of  N  and  O  well  illustrate. 

Weight.  Volume. 

N.  O.  N.  O. 

Nitrogen  protoxide     ....    N2O,                       28  16  21 

Nitrogen  dioxide N202,                     28  32  22 

Nitrogen  trioxide N2O3,                     28  48  23 

Nitrogen  tetroxide      ....    N204,                     28  64  24 

Nitrogen  pentoxide    ....    N205,                     28  80  25 

Note  that  the  proportion  of  O  by  weight  is  in  each  case 
a  multiple  of  the  first,  16.  Also  that  the  proportion  by 
volume  of  O  is  a  multiple  of  that  in  the  first  compound. 
In  this  example  the  N  remains  the  same.  If  that  had 
varied  in  the  different  compounds,  it  would  also  have 


76      LAWS   OF   DEFINITE   AND   MULTIPLE   PROPORTION. 

varied  by  a  multiple  of  the  smallest  proportion.     This  is 
true  in  all  compounds. 

115.  Law  of  Multiple  Proportion.  —  Whenever  one 
element  combines  with  another  in  more  than  one  proportion, 
it  always  combines  in  some  multiple,  one  or  more,  of  its  least 
combining  weight,  or,  if  a  gas,  of  its  least  combining  volume. 

The  least  combining  weight  of  an  element  is  its  atomic 
weight  ;  and  it  is  this  fact  of  a  least  combining  weight 
that  leads  us  to  believe  the  atom  to  be  indivisible. 

Apply  the  law  in  the  case  of  P  A  P2O3,  P2O5  ;  in  HC1O, 
HC1O2,  HC1O3,  HC1O4,  arranging  the  symbols,  weights, 
and  volumes  in  a  table,  as  above. 

4 

The  volumetric  proportions  of  each  element  in  the  oxides  of  nitro- 
gen are  exhibited  below. 

n+n-»n--[H] 

N  +  N  +  O  =  N2O 


N+N+0+0=  N202 


n+n+n+n+n+a=[H] 

N+N+0+O+O+O=  N2O4 

n+n+n+n+n+n+n=[H] 

tf  +  N  +  0  +  O+  0  +  0+  O  =  N2O5. 


CHAPTER   XXIV. 
CARBON  PROTOXIDE. 

116.  Preparation. 

Experiment  72.  —  Put  into  a  flask,  of  200CC,  5s  of  oxalic  acid  crys- 
tals, H2C2O4,  and  25CC  H2SO4.  Have  the  d.t.  pass  into  a  solution  of 
NaOH  in  a  Woulff  bot- 
tle (Fig.  31),  and  col- 
lect the  gas  over  wa- 
ter. Heat  the  flask 
slowly,  and  avoid  in- 
haling the  gas. 

117.  Tests. 

Experiment  73. — 

Remove  a  receiver  of 
the  gas,  and  try  to  light 
the  latter  with  a  splin- 
ter. Is  it  combustible,  or  a  supporter  of  (C)  combustion  ?  What  is 
the  color  of  the  flame?  When  the  combustion  ceases,  shake  up  a  lit- 
tle lime  water  with  the  gas  left  in  the  receiver.  What  gas  has  been 
formed  by  the  combustion,  as  shown  by  the  test  ?  See  page  80.  Give 
the  reaction  for  the  combustion. 

We  have  seen  that  H2SO4  has  great  affinity  for  H2O.  Oxalic  acid 
consists  of  H,  C,  0  in  the  right  proportion  to  form  H2O,  C02,  and  CO. 
H2S04  withdraws  H  and  O  in  the  right  proportion  to  form  water,  unites 
them,  and  then  absorbs  the  water,  leaving  the  C  and  O  to  combine  and  form 
CO2  and  CO.  NaOII  solution  removes  CO2  from  the  mixture,  forming 
Na2C03,  and  leaves  CO.  Write  both  reactions. 

118.  Carbon  Protoxide,  called  also  carbon  monoxide, 
carbonic  oxide,  etc.,  is  a  gas,  having  no  color  or  taste,  but 


78  CARBON   PROTOXIDE. 

possessing  a  faint  odor.  It  is  very  poisonous.  Being  the 
lesser  oxide  of  C,  it  is  formed  when  C  is  burned  in  a  limited 
supply  of  O,  whereas  CO2  is  always  produced  when  O  is 
abundant.  The  formation  of  each  is  well  shown  by  trac- 
ing the  combustion  in  a  coal  fire.  Air  enters  at  the  bot- 
tom, and  CO2  is  first  formed.  C  +  2  O  =  CO2.  As  this  gas 
passes  up,  the  white-hot  coal  removes  one  atom  of  O, 
leaving  CO.  CO2  +  C  =  2  CO.  At  the  top,  if  the  draft  be 
open,  a  blue  flame  shows  the  combustion  of  CO.  CO  + 
O  =  CO2.  The  same  reduction  of  CO2  takes  place  in  the 
iron  furnace,  and  whenever  there  is  not  enough  oxygen  to 
form  CO2,  the  product  is  CO. 

Great  care  should  be  taken  that  this  gas  does  not  escape 
into  the  room,  as  one  per  cent  has  proved  fatal.  Not  all 
of  it  is  burned  at  the  top  of  the  coal ;  and  when  the  stove 
door  is  open,  the  upper  drafts  should  be  open  also.  It  is 
the  most  poisonous  of  the  gases  from  coal ;  hence  the 
danger  from  sleeping  in  a  room  having  a  coal  fire. 

119.  Water  Gas.  —  CO  is  one  of  the  constituents  of 
"  water  gas,"  which,  by  reason  of  its  cheapness,  is  sup- 
planting gas  made  from  coal,  as  an  illuminator,  in  some 
cities.  It  is  made  by  passing  superheated  steam  over  red- 
hot  charcoal  or  coke.  C  unites  with  the  O  of  H2O,  form- 
ing CO,  and  sets  H  free,  thus  producing  two  inflamma- 
ble gases.  C  +  H2O=?  As  neither  of  these  gives  much 
light,  naphtha  is  distilled  and  mixed  with  them  in  small 
quantities  to  furnish  illuminating  power  See  page  183. 


CHAPTER   XXV. 

CARBON  DIOXIDE. 

120.  Preparation. 

Experiment  74.- — Put  into  a  t.t.,  or  a  bottle  with  a  d.t.  and  a 
thistle-tube,  10  or  20^  CaCO3,  marble  in  lumps ;  add  as  many  cubic 
centimeters  of  H2O,  and  half  as  much  HC1,  and  collect  the  gas  by 
downward  displacement  (Fig.  39).  Add  more  acid  as  needed.  CaCO3 
+  2  HC1  -  CaCl2  +  H2CO3.  H2CO3=  H2O  +  CO2.  H2CO3  is  a  very 
weak  compound,  and  at  once  breaks  up.  By  some,  its  existence  as  a 
compound  is  doubted. 

121.  Tests. 

Experiment  75.  —  (1)  Put  a  burning  and  a  glowing  stick  into  the 
t.t.  or  bottle.  (2)  Hold  the  end  of  the  d.t.  directly  against  the  flame  of 
a  small  burning  stick.  Does  the  gas  support  combustion?  (3)  Pour  a 
receiver  of  the  gas  over  a  candle  flame.  What  does  this  show  of  the 
weight  of  the  gas?  (4)  Pass  a  little  CO2  into  some  H2O  (Fig.  32),  and 
test  it  with  litmus.  Give  the  reaction  for  the  solution  of  CO2  in  H2O. 

Experiment  76.  —  Put  into  a  t.t.  5CC  of  clear  Ca(OH)2  solution, 
i.e.  lime  water;  insert  in  this  the  end  of  a  d.t. 
from  a  CO2  generator  (Fig.  32).  Notice  any  ppt. 
formed.  It  is  CaCO3.  Let  the  action  continue 
until  the  ppt.  disappears  and  the  liquid  is  clear. 
Then  remove  the  d.t.,  boil  the  clear  liquid  for  a 
minute,  and  notice  whether  the  ppt.  reappears. 


122.    Explanation. 

Ca(OH)2+CO2=CaCO3+H2O.  The 
curious  phenomena  of  this  experiment 
are  explained  by  the  solubility  of  CaCO3 
in  water  containing  COg,  and  its  insolu-  Mg. 


80  CARBON   DIOXIDE. 

bility  in  water,  having  no  CO2.  When  all  the  Ca(OH)2 
is  combined,  or  changed  to  CaCO3,  the  excess  of  CO2  unites 
with  H2O,  forming  the  weak  acid  H2CO3,  which  dissolves 
the  precipitate,  CaCO3,  and  gives  a  clear  liquid.  On 
heating  this,  H2CO3  gives  up  its  CO2,  and  CaCO3  is  re- 
precipitated,  not  being  soluble  in  pure  water.  See  page 
147. 

Lime  water,  Ca(OH)2  solution,  is  therefore  a  test  for 
the  presence  of  CO2.  To  show  that  carbon  dioxide  is 
formed  in  breathing,  and  in  the  combustion  of  C,  and  that 
it  is  present  in  the  air,  perform  the  following  experiment : 

Experiment  77.  —  (1)  Put  a  little  lime  water  into  a  t.t.,  and  blow 
into  it  through  a  piece  of  glass  tubing.  Any  turbidity  shows  what? 
(2)  Burn  a  candle  for  a  few  minutes  in  a  receiver  of  air,  then  take  out 
the  candle  and  shake  up  lime  water  with  the  gas.  (3)  Expose  some 
lime  water  in  an  e.d.  to  the  air  for  some  time. 

123.  Oxidation  in  the  Human  System.  —  Carbon  di- 
oxide, or  carbonic  anhydride,  carbonic  acid,  etc.,  CO2,  is  a 
heavy  gas,  without  color  or  odor.  It  has  a  sharp,  prickly 
taste,  and  is  commonly  reckoned  as  poisonous  if  inhaled  in 
large  quantities,  though  it  does  not  chemically  combine 
with  the  blood  as  CO  does.  Ten  per  cent  in  the  air  will 
sometimes  produce  death,  and  five  per  cent  produces 
drowsiness.  It  exists  in  minute  portions  in  the  atmos- 
phere, and  often  accumulates  at  the  bottom  of  old  wells 
and  caverns,  owing  to  its  slow  diffusive  power.  Before 
going  down  into  one  of  these,  the  air  should  always  be 
tested  by  lowering  a  lighted  candle.  If  this  is  extin- 
guished, there  is  danger.  CO2  is  the  deadly  "choke 
damp  "  after  a  mine  explosion,  CH4  being  converted  into 
CO2  and  H2O ;  a  great  deal  is  liberated  during  vol- 
canic eruptions,  and  it  is  formed  in  breathing  by  the 


CARBON   DIOXIDE.  81 

union  of  O  in  the  air  with  C  in  the  system.  This  union 
of  C  and  O  takes  place  in  the  lungs  and  in  all  the  tissues 
of  the  body,  even  on  the  surface.  Oxygen  is  taken  into 
the  lungs,  passes  through  the  thin  membrane  into  the 
blood,  forms  a  weak  chemical  union  with  the  red  corpus- 
cles, and  is  conveyed  by  them  to  all  parts  of  the  system. 
Throughout  the  body,  wherever  necessary,  C  and  H  are 
supplied  for  the  O,  and  unite  with  it  to  form  CO2  and 
H2O.  These  are  taken  up  by  the  blood  though  they  do  not 
form  a  chemical  union  with  it,  are  carried  to  the  lungs, 
and  pass  out,  together  with  the  unused  N  and  surplus  O. 
The  system  is  thus  purified,  and  the  waste  must  be  sup- 
plied by  food.  The  process  also  keeps  up  the  heat  of 
the  body  as  really  as  the  combustion  of  C  or  P  in  O  pro- 
duces heat.  The  temperature  of  the  body  does  not  vary 
much  from  99°  F.,  any  excess  of  heat  passing  off  through 
perspiration,  and  being  changed  into  other  forms  of  energy. 
If,  as  in  some  fevers,  the  temperature  rises  above  about 
105°  F.,  the  blood  corpuscles  are  killed,  and  the  person 
dies.  During  violent  exercise  much  material  is  consumed, 
circulation  is  rapid,  and  quick  breathing  ensues.  Oxygen 
is  necessary  for  life.  A  healthy  person  inhales  plenti- 
fully ;  and  this  element  is  one  of  nature's  best  reme- 
dies for  disease.  Deep  and  continued  inhalations  in  cold 
weather  are  better  than  furnace  fires  to  heat  the  system. 
All  animals  breathe  O  and  exhale  CO2.  Fishes  and  other 
aquatic  animals  obtain  it,  riot  by  decomposing  H2O,  but 
from  air  dissolved  in  water.  Being  cold-blooded,  they 
need  relatively  little ;  but  if  no  fresh  water  is  supplied  to 
those  in  captivity,  they  soon  die  of  O  starvation. 

124.    Oxidation   in   Water.  —  Swift-running    streams 
are  clear  and  comparatively  pure,  because  their  organip 


82  CARBON   DIOXIDE. 

impurities  are  constantly  brought  to  the  surface  and  oxi- 
dized, whereas  in  stagnant  pools  these  impurities  accumu- 
late. Reservoirs  of  water  for  city  supply  have  sometimes 
been  freed  from  impurities  by  aeration,  i.e.  by  forcing 
air  into  the  water. 

125.  Deoxidation  in  Plants. — Since  CO2  is  so   con- 
stantly poured  into  the  atmosphere,  why  does  it  not  accu- 
mulate there  in  large  quantity?     Why  is  there  not  less  free 
O  in  the  air  to-day  than  there  was  a  thousand  years  ago  ? 
The  answer  to  these  questions  is  found  in  the  growth  of 
vegetation.     In  the  leaf  of  every  plant  are  thousands  of 
little  chemical  laboratories;   CO2  diffused  in  small  quan- 
tities in  the  air  passes,  together  with  a  very  little  H2O,  into 
the  leaf,  usually  from  its  under  side,  and  is  decomposed 
by  the  radiant  energy  of  the  sun.    The  C  is  built  into  the 
woody  fiber  of  the  tree,  and  the  O  is  ready  to  be  re-breathed 
or  burned  again.      CO2  contributes  to  the  growth  of  plants, 
O  to  that  of  animals ;  and  the  constituents  of  the  atmos- 
phere vary  little  from  one  age  to  another.     The  compensa- 
tion of   nature  is  here  well   shown.      Plants   feed   upon 
what  animals   discard,   transforming  it  into  material  for 
the  sustenance  of  the  latter,  while  animals  prepare  food  for 
plants.     All  the  C  in  plants  is  supposed  to  come  from  the 
CO2  in    the    atmosphere.      Animals  obtain   their   supply 
from  plants.     The  utility  of  the  small  percentage  of  CO2 
in  the  air  is  thus  seen. 

126.  Uses.  —  CO2  is    used   in    making    "soda-water," 
and  in  chemical  engines  to  put  out  fires  in  their  early 
stages.     In    either  case  it  may  be    prepared  by  treating 
Na2CO3  or  CaCO3  with  H2SO4.     Give  the  reactions.     On  a 
small  scale  CO2  is  made  from  HNaCO8. 


CARBON   DIOXIDE.  83 

CO2  has  a  very  weak  affinity  for  water,  but  probably 
forms  with  it  H2CO3.  Much  carbon  dioxide  can  be  forced 
into  water  under  pressure.  This  forms  soda-water,  which 
really  contains  no  soda.  The  justification  for  the  name 
is  the  material  from  which  it  is  sometimes  made.  Salts 
from  H2CO3,  called  carbonates,  are  numerous,  Na2CO3  arid 
CaCO3  being  the  most  important. 


CHAPTER   XXVI. 

OZONE. 

127.  Preparation. 

Experiment  78.  —  Scrape  off  the  oxide  from  the  surface  of  a  piece 
of  phosphorus  2cm  long,  put  it  into  a  wide-mouthed  bottle,  half  cover 
the  P  with  water,  cover  the  bottle  with  a  glass,  and  leave  it  for  half  an 
hour  or  more. 

128.  Tests. 

Experiment  79.  —  Remove  the  glass  cover,  smell  the  gas,  and  hold 
in  it  some  wet  iodo-starch  paper.  See  page  104.  Look  for  any  blue 
color.  Iodine  has  been  set  free,  according  to  the  reaction,  2  KI+  O3  — 
K2O  +  O2  +  I2,  and  has  imparted  a  blue  color  to  the  starch,  and 
ordinary  oxygen  has  been  formed.  Why  will  not  oxygen  set  iodine 
free  from  KI  ?  What  besides  ozone  will  liberate  it  ?  See  page  104. 

129.  Ozone,  oxidized   oxygen,   active   oxygen,   etc.,  is 
an  allotropic  form  of  O.     Its  molecule  is  O3,  while  that 
of  ordinary  oxygen  is  O2. 


3  atoms    _     1  raol. 
oxygen    ~       ozone. 


Three  atoms  of  oxygen  are  condensed  into  the  space  of 
two  atoms  of  ozone,  or  three  molecules  of  O  are  condensed 
into  two  molecules  of  ozone,  or  three  liters  of  O  are  con- 
densed into  two  liters  of  ozone. 

Ozone  is  thus  formed  by  oxidizing  ordinary  oxygen. 
O2  -f  O  —  O3.  This  takes  place  during  thunder  storms 
and  in  artificial  electrical  discharges.  The  quantity  of 


OZONE.  85 

ozone  produced  is  small,  five  per  cent  being  the  maximum, 
and  the  usual  quantity  is  far  less  than  that. 

Ozone  is  a  powerful  oxidizing  agent,  and  will  change  S, 
P,  and  As  into  their  ic  acids.  Cotton  cloth  was  formerly 
bleached,  and  linen  is  now  bleached,  by  spreading  it  on  the 
grass  and  leaving  it  for  weeks  to  be  acted  on  by  ozone, 
which  is  usually  present  in  the  air  in  small  quantities,  es- 
pecially in  the  country.  Ozone  is  a  disinfectant,  like  other 
bleaching  agents,  and  serves  to  clear  the  air  of  noxious 
gases  and  germs  of  infectious  diseases.  So  much  ozone  is 
reduced  in  this  way  that  the  air  of  cities  contains  less  of  it 
than  country  air.  A  third  is  consumed  in  uniting  with  the 
substance  which  it  oxidizes,  while  two-thirds  are  changed 
into  oxygen,  as  in  Experiment  79. 

It  is  unhealthful  to  breathe  much  ozone,  but  a  little 
in  the  air  is  desirable  for  disinfection. 

Ozone  will  cause  the  inert  N  of  the  air  to  unite  with  H, 
to  form  ammonia.  No  other  agent  capable  of  doing  this 
is  known,  so  that  all  the  NH3  in  the  air,  in  fact  all  am- 
monium compounds  taken  up  by  plants  from  soils  and 
fertilizers,  may  have  been  made  originally  through  the 
agency  of  ozone.  At  a  low  temperature  ozone  has  been 
liquefied.  It  is  then  distinctly  blue. 

Electrolysis  of  water  is  the  best  mode  of  preparing  this 
substance  in  quantity.  When  prepared  from  P  it  is  mixed 
with  P2O3. 


CHAPTER   XXVII. 

CHEMISTRY  OF  THE  ATMOSPHERE. 

130.  Constituents.  —  The    four   chief   constituents  of 
the  atmosphere  are  N,  O,  H2O,  CO2,  in  the  order  of  their 
abundance.     What  experiments  show  the  presence  of  N, 
O,  and  CO2in  the  air?    See  pages  22,  80.     Set  a  pitcher  of 
ice  water  in  a  warm  room,  and  the  moisture  that  collects  on 
the  outside  is  deposited  from  the  air.      This  shows  the 
presence  of  H2O.     Rain,  clouds,  fog,  and  dew  prove  the 
same.     H2SO4  and  CaCl2,  on  exposure  to  air,  take  up  water. 
Experiment  18   shows  that   there   is   not  far  from   four 
times  as  much  N  as  O  by  volume  in  air.     Hence  if  the 
atmosphere  were  a  compound  of  N  and  O,  arid  the  propor- 
tion of  four  to  one  were  exact,  its  symbol  would  be  N4O. 

• 

131.  Air  not  a  Compound.  --  The  following  facts  show 

that  air  is  not  a  compound,  but  rather  a  mixture  of  these 


1.  The  proportion  of  N  and  O  in  the  air,  though  it 
does  not  vary  much,  is  not  always  exactly  the  same.     This 
could  not  be  true  if  it  were  a  compound.     Why  ? 

2.  If  N4O  were  dissolved  in  water,  the  N  would  be  four 
times  the  O  in  volume ;  but  when  air  is  dissolved,  less  than 
twice  as  much  N  as  O  is  taken  up. 

3.  No   heat   or   condensation   takes   place   when    four 
measures  of  N  are  brought  in  contact  with  one  of  O.     It 
cannot  then  be  N4O,  for  the  vapor  density  of  N4O  would 


CHEMISTRY  OF  THE   ATMOSPHERE.  87 


be  36  —  i.e.  (14  X  4  +  16)  -f-  2  ;  but  that  of  air  is  14£  nearly 
—  i.e.  (14  X  4  +  16)  ^-5.  See  page  108.  Analysis  shows 
about  79  parts  of  N  to  21  parts  of  O  by  volume  in  air. 

132.  Water.  —  The  volume  of  H2O,  watery  vapor,  in 
the  atmosphere  is  very  variable.      Warm   air  will  hold 
more  than  cold,  and  at  any  temperature  air  may  be  near 
saturation,  i.e.  having  all  it  will  hold  at  that  temperature, 
or  it  may  have  little.    But  some  is  always  present  ;  though 
the  hot  desert  winds  of  North  Africa  are  not  more  than 
TaT  saturated.    A  cubic  meter  of  air  at  25°,  when  saturated, 
contains  more  than  22g  of  water. 

133.  Carbon  Dioxide.  —  Carbon  dioxide  does  not  make 
up  more  than  three  or  four  parts  in  ten  thousand  of  the 
air;   but,  in  the  whole  of  the  atmosphere,  this   gives   a 
very  large  aggregate.     Why  does  not  CO2  form  a  layer 
below  the  O  and  N  ?     See  page  114. 

134.  Other  Ingredients.  —  Other  substances  are  found 
in  the  air  in  minute  portions,  e.g.  NH3  constitutes  nearly 
one-millionth.      Air  is  also  impregnated  with  living  and 
dead  germs,  dust   particles,  unburned   carbon,  etc.,  but 
these  for  the  most  part  are  confined  to  the  portion  near 
the  earth's  surface.     In  pestilential  regions  the  germs  of 
disease  are  said  sometimes  to  contaminate  the  air  for  miles 
around.     See  page  195. 


CHAPTER   XXVIII. 
THE    CHEMISTRY  OF   WATER. 

135.  Pure  Water.  —  Review  the  experiments  for  elec- 
trolysis, and  for  burning  H.     Pure  water  is  obtained  by 
distillation. 

Experiment  80.  —  Provide  a  glass  tube  40  or  50cm  long  and  3 
or  4cm  in  diameter.  Fit  to  each  end  a  cork  with  two  perforations, 

through  one  of  which  a  long 
tube  passes  the  entire  length  of 
the  larger  tube  (Fig.  32a) .  Con- 
nect one  end  of  this  with  a  flask 
of  water  arranged  for  heating ; 
pass  the  other  end  into  an  open 
receptacle  for  collecting  the 
distilled  Ivater.  Into  the  other 
perforations  lead  short  tubes,  — 
the  one  for  water  to  flow  into 
the  large  tube  from  a  jet ;  the 
other,  for  the  same  to  flow  out. 

This  condenses  the  steam  by  circulating  cold  water  around  it.  The 
apparatus  is  called  a  Liebig's  condenser.  Put  water  into  the  flask, 
boil  it,  and  notice  the  condensed  liquid.  It  is  comparatively  pure 
water;  for  most  of  the  substances  in  solution  have  a  higher  boiling- 
point  than  water,  and  are  left  behind  when  it  is  vaporized. 

136.  Test. 

Experiment  81.  — Test  the  purity  of  distilled  water  by  slowly 
evaporating  a  few  drops  on  Pt  foil  in  a  room  free  from  dust.  There 
should  be  no  spot  or  residue  left  on  the  foil.  Test  in  the  same  way 
undistilled  water. 


THE   CHEMISTRY   OF  "WATER.  89 

137.  Water   exists    in    Three    States,  —  solid,  liquid, 
and  vaporous.     It  freezes  at  0°,  suddenly  expanding  con- 
siderably as  it  passes  into  the  solid  state.      It  boils,  i.e. 
overcomes  atmospheric  pressure  and  is  vaporized,  at  100° 
(760Inm  pressure).      If  the  pressure  is  greater,  the   boil- 
ing-point is  raised,  i.e.  it  takes  a  higher  temperature  to 
overcome  a  greater  pressure.    If  there  be  less  pressure,  as 
on  a  mountain,  the  boiling-point  is  lowered  below  100°. 
Salts  dissolved  in  water  raise  its  boiling-point,  and  lower 
its  freezing-point  to  an  extent  depending  on  the  kind  and 
quantity  of  the  salt.     Water,  however,  evaporates  at  all 
temperatures,  even  from  ice. 

Pure  water  has  no  taste  or  smell,  and,  in  small  quan- 
tities, no  color.  It  is  rarely  if  ever  found  on  the  earth. 
What  is  taken  up  by  the  air  in  evaporation  is  nearly 
pure  ;  but  when  it  falls  as  rain  or  snow,  impurities  are 
absorbed  from  the  atmosphere.  Water  falling  after  a 
long  rain,  especially  in  the  country,  is  tolerably  free 
from  impurities.  Some  springs  have  also  nearly  pure 
water ;  but  to  separate  all  foreign  matter  from  it,  water 
must  be  distilled.  Even  then  it  is  liable  to  contain  traces 
of  ammonia,  or  some  other  substance  which  vaporizes  at  a 
lower  temperature  than  water. 

138.  Sea- Water.  —  The  ocean  is  the   ultimate  source 
of  all  water.      From  it  and  from  lakes,  rivers,  and  soils, 
water  is  taken  into  the  atmosphere,  falls  as  rain  or  snow, 
and   sinks   into   the   ground,   reappearing  in  springs,   or 
flowing  off  in  brooks  and  rivers  to  the  ocean  or  inland 
seas.      Ocean  water  must  naturally  contain  soluble  salts ; 
and   many   salts   which   are   not   soluble   in   pure    water 
are  dissolved  in  sea-water.     In  fact,  there  is  a  probability 
that  all  elements  exist  to  some  extent  in  sea- water,  but 


90  THE  CHEMISTRY  OF   WATER. 

many  of  them  in  extremely  minute  quantities.  Sodium 
and  magnesium  salts  are  the  two  most  abundant,  and  the 
bitter  taste  is  due  to  MgSO4  and  MgCl2.  A  liter  of  sea- 
water,  nearly  1000g,  holds  over  37g  of  various  salts,  29  of 
which  are  NaCl.  See  Hard  Water,  page  147. 

139.  River  Water.  —  River  water  holds   fewer   salts, 
but  has  a  great  deal  of  organic  matter,  living  and  dead, 
derived  from  the   regions   through  which  it  flows.      To 
render  this  harmless  for  drinking,  such  water  should  be 
boiled,  or  filtered   through   unglazed   porcelain.     Carbon 
filters  are  now  thought  to  possess   but   little   virtue  for 
separating  harmful  germs. 

140.  Spring-  Water.  —  The  water  of  springs  varies  as 
widely  in  composition  as  do  the  rocks  whence  it  bubbles 
forth.      Sulphur  springs  contain  much  H2S ;    many  gey- 
sers hold  SiO2  in  solution:  chalybeate  waters  have  com- 
pounds of  Fe;  others  have  Na2SO4,  MgSO4,  NaCl,  etc. 


CHAPTER   XXIX. 

THE    CHEMISTRY   OF  FLAME. 

141.  Candle  Flame. 

Experiment  82. —  Examine  a  candle  flame,  holding  a  dark  ob- 
ject behind  it.  Note  three  distinct  portions  :  (1)  a  colorless  interior 
about  the  wick,  (2)  a  yellow  light-giving  portion  beyond  that,  (3)  a 
thin  blue  envelope  outside  of  all,  and  scarcely  discernible.  Hold  a 
small  stick  across  the  flame  so  that  it  may  lie  in  all  three  parts,  and 
observe  that  no  combustion  takes  place  in  the  inner  portion. 

142.  Explanation.  —  A  candle  of  paraffine,  or  tallow, 
is  chiefly  composed  of  compounds  of  C  and  H,  in  the  solid 
state.      The  burning  wick  melts  the  solid;  the  liquid  is 
then  drawn  up  by  the  wick  till  the  heat  vaporizes  and 
decomposes  it,  and  O  of  the  air  comes  in  contact  with 
the  outer  heated  portion  of  gas,  and  burns  it  completely. 
Air  tends  to  penetrate  the  whole  body  of  the  flame,  but 
only  N  can  pass  through  uncombined,  for  the  O  that  is 
left  after  combustion  in  the  outer  portion  seizes  upon  the 
compounds  of  C  and  H  in  the  next,  or  yellow,  part.     There 
is  not  enough  O  here  for  complete  combustion;    at  this 
temperature  H  burns  before  C,  and  the  latter  is  set  free. 
In  that  state  it  is  of  course  a  solid.     Now  an  incandescent 
solid,  or  one  glowing  with  heat,  gives  light,  while  the  com- 
bustion of  a  gas  gives  scarcely  any  light,  though  it  may  pro- 
duce great  heat.     While  C  in  the  middle  flame  is  glowing, 
during  the  moment  of  its  dissociation  from  H,  it  gives 


92  THE    CHEMISTRY   OF    FLAME. 

light.  In  the  outer  flame  the  temperature  is  high  enough 
to  burn  entirely  the  gaseous  compounds  of  C  and  H  to- 
gether, so  that  no  solid  C  is  set  free,  and  hence  no  light  is 
given  except  the  faint  blue.  No  combustion  takes  place 
in  the  inner  blue  cone,  because  no  O  reaches  there. 

By  packing  a  wick  into  a  cylindrical  tin  cup  5  or  10cm  high  and  4cm 
in  diameter,  containing  alcohol,  and  lighting  it,  gunpowder  can  be  held  in 
the  middle  of  the  flame  in  a  def .  spoon,  without  burning.  This  shows  the 
low  temperature  of  that  portion.  Burning  P  will  also  be  extinguished, 
thus  showing  the  exclusion  of  O. 

143.    Bunsen  Flame. 

Experiment  83.  —  Examine  a  .Bunsen  burner.  Unscrew  the  top, 
and  note  the  orifices  for  the  admission  of  gas  and  of  air.  Make  a  draw- 
ing. Replace  the  parts ;  then  light  the  gas  at  the  top,  opening  the  air- 
holes at  the  base.  Notice  that  the  flame  burns  with  very  little  color. 
Try  to  distinguish  the  three  parts,  as  in  the  candle  flame.  These  parts 
can  best  be  seen  by  allowing  direct  sunlight  to  fall  on  the  flame  and 
observing  its  shadow  on  a  white  ground.  Make  a  drawing  of  the 
flame.  Hold  across  it  a  Pt  wire  and  note  at  what  part  the  wire  glows 
most.  Also  press  down  on  the  flame  for  an  instant  with  a  card- 
board or  piece  of  paper ;  remove  before  it  takes  fire,  and  notice  the 
charred  circle.  Put  the  end  of  a  match  into  the  blue  cone,  and  note 
that  it  does  not  burn.  Put  the  end  of  a  Pt  wire  into  this  blue 
cone,  and  observe  that  it  glows  when  near  the  top  of  the  cone.  What 
do  these  experiments  show?  Ascertain  whether  this  inner  portion 
contains  a  combustible  material,  by  holding  in  it  one  end  of  a  small 
d.t.,  and  trying  to  ignite  any  gas  escaping  at  the  other  end.  It  should 
burn.  This  shows  that  no  combustion  takes  place  in  the  interior  of 
the  flame,  because  sufficient  free  O  is  not  present. 

Next,  close  the  air-holes,  and  note  that  the  flame  is  yellow  and  gives 
much  light.  From  this  we  infer  the  presence  of  solid  particles  in  an 
incandescent  state.  But  these  could  not  come  from  the  air.  They 
must  be  C  particles  which  have  been  set  free  from  the  C  and  H  com- 
pounds of  the  gas,  just  as  in  the  candle  flame.  The  smoke  that  rises 
proves  this.  Hold  an  e.d.  in  the  flame  and  collect  some  C.  Try  the 
same  with  the  air-holes  open. 


THE    CHEMISTRY    OF   FLAME. 


93 


144.  Light  and  Heat  of  Flame.  —  Which  of  the  two 
flames  is  hotter,  the  one  with  the  air-holes  open,  or  that 
with  them  closed  ?  Evidently  the  former ;  for  air  is  drawn 
in  and  mixes  with  the  gas  as  it  rises  in  the  tube,  and,  on 
reaching  the  flame  at  the  top,  the  two  are  well  mingled, 
and  the  gaseous  compounds  of  C  and  H  burn  at  so  high  a 
temperature  that  solid  C  is  not  freed ;  hence  there  is  little 
light.  On  closing  the  air-holes,  no  O  can  reach  the  flame 
except  from  the  outside,  and  the  heat  is  much  less  intense. 


Fig.  33. 


Fig.  34. 


The  H  burns  first,  and  sets  the  C  free,  which,  while  glow- 
ing, gives  the  light.  This  again  illustrates  the  facts  (1) 
that  flame  is  caused  by  burning  gas ;  (2)  that  light  is  pro- 
duced by  incandescent  solids.  Charcoal,  coke,  and  anthra- 
cite coal  burn  without  flame,  or  with  very  little,  because  of 
the  absence  of  gases. 

145.    Temperature  of  Combustion. 

Experiment  84.  —  Light  a  Bunsen  flame,  with  the  basal  orifices 
open,  and  hold  over  it  a  fine  wire  gauze.  Notice  that  the  flame  does 
pot  rise  above  the  gau?e,  Extinguish  the  light,  and  try  to  ignite  the 


94 


THE   CHEMISTRY   OF   FLAMM. 


gas  above  the  gauze,  holding  the  latter  within  5  or  6cm  of  the  burner 
tube.     Notice  that  it  does  not  burn  below  the  gauze  (Fig.  33). 

Gas  and  O  are  both  present.  Evidently,  then,  the  only 
condition  wanting  for  combustion  is  a  sufficiently  high 
temperature.  The  gauze  cools  the  gas  below  its  kindling- 
point. 

This  principle  is  made  use  of  in  the  miner's  lamp  of  Davy  (Fig.  34). 
In  coal  mines  a  very  inflammable  gas,  CH4,  called  fire-damp,  issues  from 
the  coal.  If  this  collects  in  large  quantities  and  mixes  with  O  of  the  air,  a 
kindling-point  is  all  that  is  needed  to  make  a  violent  explosion.  An  ordi- 
nary lamp  would  produce  this,  but  the  gauze  lamp  prevents  it ;  for,  though 
the  inside  may  be  filled  with  burning  gas,  CH4,  the  flame  cannot  communi- 
cate with  the  outside. 


Fig.  35. 


Fig.  36. 

a,  reducing  flame.    6,  oxidizing  flame. 


146.  Oxidizing  and  Reducing  Flames.  —  The  hottest 
part  of  a  Bunsen  flame  is  just  above  the  inner  blue  cone 
(5,  Fig.  86).  Evidently  there  is  more  O  at  that  point. 
If  a  reducing  agent,  i.e.  a  substance  which  takes  up  O, 
be  put  into  this  part  of  the  flame,  the  latter  will  remove 
the  O  and  appropriate  it,  forming  an  oxide.  Cu  heated 
there  would  become  copper  oxide.  This  part  is  called 
the  oxidizing  flame. 


THE   CHEMISTRY    OF   FLAME. 


95 


'The  inner  blue  part  of  the  Bunsen  flame  is  devoid  of  O. 
It  ought  to  remove  O  from  an  oxidizing  agent,  i.e.  a  sub- 
stance which  supplies  O.  If  copper  oxide  be  heated  there 
(a.  Fig.  36)  by  means  of  a  mouth  blow-pipe  (Fig.  35),  the 
flame  will  appropriate  the  O  and  leave  the  copper.  This 
is  called  the  reducing  flame.  Only  the  upper  part  of  this 
blue  central  cone  has  heat  enough  to  act  in  this  way.  By 
using  a  prepared  piece  of  metal,  to  make  the  flame  thin 
and  to  shut  off  the  air,  and  then  blowing  the  flame  with  a 
blow-pipe,  greater  strength  can  be  obtained  in  both  oxidiz- 
ing and  reducing  flames  (Fig.  36). 

147.    Combustible  and  Supporter  Interchangeable. — 

H  was  found  to  burn  in  O.  H  was  the  combustible,  O 
the  supporter.  Would  O  itself  burn  in  H  ?  —  i.e.  would 
the  combustible  become  the  supporter,  and  the  supporter 
the  combustible  ?  As  il- 
luminating gas  consists 
largely  of  H,  and  as  air 
is  part  O,  we  may  try  the 
experiment  with  gas  and 
air.  Gas  will  burn  in 
air.  Will  air  burn  in  gas  ? 

Experiment    85.  —  Fit    a 

cork  with  two  holes  in  it  to 
the  large  end  of  a  lamp  chim- 
ney. Through  each  hole  pass 
a  short  piece  of  tubing,  and 
connect  one  of  these  with  a 
rubber  tube  leading  to  a  gas- 
jet.  Pass  a  metallic  tube,  long  enough  to  reach  the  top  of  the  chimney, 
through  the  other,  so  that  it  will  move  easily  up  and  down.  Turn 
on  the  gas,  and  light  it  at  the  top  of  the  chimney.  Hold  the  end 
qf  the  tube  passing  through  the  cork  in  the  flame  for  a  minute, 


Fig.  37  «. 


96 


THE   CHEMISTRY   OF   FLAME. 


Fig.  38. 


then  draw  it  down  to  the  middle  of  the  chimney  (Fig.  37,  a)  and  finally 
slowly  remove  it  (&).  Note  that  O  from  the  air  is  burning  in  the  gas. 
Which  is  the  supporter,  and  which  the  com- 
bustible in  this  case?  O  will  burn  equally 
well  in  an  atmosphere  of  H,  as  can  be  shown 
by  experiment. 

148.     Explosive       Mixture      of 
Gases. 

Experiment  86.  —  Slowly  turn   down 
the  burning  gas  of  a  Bunseri  lamp,  having 
the   orifices  open,  and  notice  that  it  sud- 
denly explodes  and  goes  out  at  the  top, 
but  now  burns  at  the  base.     As  the  gas  was 
gradually  turned    off,    more    air    became 
mixed  with  it,  until  there  was  the  right 
proportion  of  each  gas  for  an  explosion. 
Figure   38   shows  the  same  thing.     Light 
the  gas  at  the  top  a,  when  the  tube  c  covers 

the  jet  b.     Then  gradually  raise  the  tube  c.     At  a  certain  place  there 
is  the  same  explosion  as  with  the  lamp. 

149.  Generalizations.  —  These  experiments  show  (1) 
that  three  conditions  are  necessary  for  combustion,  —  a 
combustible,  a  supporter,  and  a  burning  temperature 
wjiich  varies  for  different  substances.  Given  these,  "  a 
fire "  always  results.  The  conditions  for  "  spontaneous 
combustion "  do  not  differ  from  those  of  any  combus- 
tion. See  Experiments  34,  112,  113,  114.  (2)  That 
combustible  and  supporter  are  interchangeable.  If  H 
burns  in  O,  O  will  burn  in  H,  the  product  being  the  same 
in  each  case.  (3)  For  any  combustion  there  must  be 
a  certain  proportion  of  combustible  and  of  supporter. 
Twenty  per  cent  of  CO2  in  the  air  dilutes  the  O  to  such 
an  extent  that  C  will  not  burn.  Hence  the  utility  of  the 
chemical  engine  for  putting  out  fires.  (4)  When  two 


THE    CHEMISTRY   OF   FLAME.  97 

gases,  a  combustible  and  a  supporter,  are  mixed  in  the 
requisite  proportion,  they  form  an  explosive  mixture, 
needing  only  the  kindling  temperature  to  unite  them. 

Chemical  combination  is  always  accompanied  by  dis- 
engagement of  heat.  Chemical  dissociation  is  always 
accompanied  by  absorption  of  heat.  The  disengagement, 
or  the  absorption,  is  not  always  evident  to  the  senses. 

Combustion  is  the  chemical  combination  of  two  or  more 
substances  with  the  self-evident  disengagement  of  great 
heat,  and  usually  of  light. 

The  temperature  of  ignition  varies  greatly  with  differ- 
ent substances.  PH3  burns  spontaneously  at  the  usual 
temperatures  of  the  air.  P  takes  fire  at  60°,  but  even  at 
10°  it  oxidizes  with  rapidity  enough  to  produce  phospho- 
rescence. The  vapor  of  CS2  may  be  set  on  fire  by  a  glass 
rod  heated  to  150°,  but  a  red-hot  iron  will  not  ignite  illu- 
minating gas. 

Spontaneous  combustion  often  takes  place  in  woolen  or 
cotton  rags  which  have  been  saturated  with  oil.  The  oil 
rapidly  absorbs  O,  and  sets  fire  to  the  cloth.  This  is 
thought  to  be. the  origin  of  some  very  destructive  fires. 


CHAPTER   XXX. 


CHLORINE. 


15O.    Preparation. 


Experiment  87.  —  Put  into  a  t.t.  5&  of  fine  granular  MnO2  and 
10CC  HC1.     Apply  heat  carefully,  and  collect  the  gas  by  downward 

displacement  in  a  receiver  loosely 
covered  with.paper  (Fig.  39).  Add 
more  HC1  if  needed.  Have  a  good 
draft  of  air,  and  do  not  inhale 
the  gas.  If  you  have  accidentally 
breathed  it,  inhale  alcohol  vapor 
from  *a  handkerchief  ;  alcohol  has 
great  affinity  for  Cl.  Note  the 
color  of  the  gas,  and  compare  its 
weiht  with  that  of  air. 


MnO 


2  HO 


+  2  Cl.    How  much  Cl  can  be  sepa- 
rated with  58  MnO2? 

If  preferred,  a  flask  may  be  used  for  a  generator  instead  of  a  t.t. 
Cl  can  be  obtained  directly  from   NaCl  by  adding 
H2SO4  (which  produces  HC1)  and  MnO2.     2  NaCl  + 
2  H2SO4  +  MnO2  =  MnSO4  +  Na2SO4  +  2  H2O  +  2  Cl. 
Try  the  experiment,  using  a  t.t.  and  adding  water. 

151.  Cl  from  Bleaching-Powder. 

Experiment  88.  —  Put  a  few  grams  of  bleaching- 
powder  into  a  small  beaker,  and  set  this  into  a  larger 
one.  Cover  the  latter  with  pasteboard  or  paper,  through 
which  passes  a  thistle-tube  reaching  into  the  small 
beaker  (Fig.  40).  Pour  through  the  tube  a  little 
H2SO4  diluted  with  its  volume  of  H2O.  Fig  40. 

152.  Chlorine  Water.  —  A  solution  of  Cl  in  water  is 
often  useful,  and  may  be  made  as  follows :  — 


/, 

-,. 

Experiment  89.  —  To  3  or  4  crystals  of  KC1O3  add  a. few  drops  of 
HC1.  Heat  a  minute,  and  when  the  gas  begins  to  disengage,  pour  in 
10CC  H2O,  which  dissolves  the  gas.  2  KC1O3  +  4  HC1  =  2  KC1  +  C12O4 
+  2  H2O  +  2  Cl. 

153.  Bleaching-  Properties. 

Experiment  90.  —  Put  into  a  receiver  of  Cl,  preferably  before 
generating  it,  two  pieces  of  Turkey  red  cloth,  one  wet,  the  other  dry; 
a  small  piece  of  printed  paper  and  a  written  one ;  also  a  red  rose 
or' a  green  leaf,  each  wet.  Note  from  which  the  color  is  discharged. 
If  it  is  not  discharged  from  all,  put  a  little  H2O  into  the  receiver, 
shake  it  well,  and  state  what  ones  are  bleached. 

Experiment  91.  —  (1)  Add  5CC  of  Cl  water  to  5CC  of  indigo  solu- 
tion. (2)  Treat  in  the  same  way  5CC  K2Cr2O7  (potassium  dichromate) 
solution,  and  record  the  results. 

Indigo,  writing-ink,  and  Turkey  red  or  madder,  are 
vegetable  pigments ;  printer's  ink  contains  C,  and  K2Cr2O7 
is  a  mineral  pigment.  State  what  coloring  matters  Cl  will 
bleach. 

154.  Disinfecting  Power. 

Experiment  92.  —  Pass  a  little  H2S  gas  from  a  generator  (page  120) 
into  a  t.t.  containing  Cl  water.  Look  for  a  deposit  of  S.  Notice  that 
the  odor  of  H2S  disappears.  H2S  +  2  Cl  =  2  HC1  +  S, 

155.  A  Supporter  of  Combustion. 

Experiment  93.  —  Sprinkle  into  a  receiver  of  Cl  a  very  little  fine 
powder  or  filings  of  Cu,  As,  or  Sb,  and  notice  the  combustion.  Ob- 
serve that  here  is  a  case  of  combustion  in  which  O  does  not  take 
part.  Chlorides  of  the  metals  are  of  course  formed.  Write  the  re- 
actions. See  whether  Cl  will  support  the  combustion  of  paper  or 
of  a  stick  of  wood. 

Experiment  94.  —  Warm  2  or  3CC  of  oil  of  turpentine  (C10H16)  in 
an  evaporating-dish ;  dip  a  piece  of  tissue  paper  into  it,  and  very 
quickly  thr.ust  this  into  a  receiver  of  Cl.  It  should  take  fire  and 


100  CHLORINE. 

deposit  carbon.     C10H16+  16  Cl  =  ?     Test  the  moisture  on  the  sides  of 
the  receiver  with  litmus.     Clean  the  receiver  with  a  little  petroleum. 

Experiment  95.  —  Prepare  a  H  generator  with  a  lamp-tube  bent 
as  in  Figure  41.  Light  the  H,  observing  the  cautions  in  Experiment 
23,  and  when  well  burning,  lower  the  flame 
into  a  receiver  of  Cl.  Observe  the  change  of 
color  which  the  flame  undergoes  as  it  comes 
in  contact  with  Cl.  Give  the  reaction  for  the 
burning.  Test  with  litmus  any  moisture  on 
the  sides  of  the  receiver.  A  mixture  of  Cl 
and  H,  in  direct  sunlight  combines  with  ex- 
plosive violence  ;  whereas  in  diffused  sunlight 
it  combines  slowly,  and  in  darkness  it  does 
not  combine.  From  these  experiments  state 
the  chief  properties  of  Cl,  and  what  combus- 
tion it  will  support. 


Soupces    an(i 

great  ;source  of  Cl  is  NaCl,  though  it  is  often  made  from 
HC1.  Its  chief  use  is  in  making  bleaching-powder,  one 
pound  of  which  will  bleach  300  to  500  pounds  of  cloth. 
Cl  is  very  easily  liberated  from  this  powder  by  a  dilute 
acid,  or,  slowly,  by  taking  moisture  from  the  air.  Hence 
its  use  as  a  disinfectant  in  destroying  noxious  gases 
and  the  germs  of  infectious  diseases.  Cl  attacks  organic 
matter  and  germs  as  it  does  the  membrane  of  the  throat 
or  lungs,  owing  to  its  affinity  for  H. 

Cl  is  the  best  bleaching  agent  for  cotton  goods.  It  is 
not  suitable  for  animal  materials,  such  as  silk  and  wool,  as 
it  attacks  their  fiber.  It  does  not  discharge  either  mineral 
or  carbon  colors.  The  chemistry  of  bleaching  is  obscure. 
As  dry  material  will  not  bleach,  Cl  seems  to  unite  with  H 
in  H2O  and  to  set  O  free.  The  O  then  unites  with  some 
portion  of  the  coloring  matter,  oxidizing  it,  and  breaking 
up  its  molecule.  Colors  bleached  by  Cl  cannot  be  restored. 


CHAPTER   XXXI. 
BROMINE. 

Examine  bromine,  potassium  bromide,  sodium  bromide,  magne- 
sium bromide. 

157.  Preparation. 

Experiment  96.  —  Pulverize  2  or  3s  KBr,  and  mix  it  with  about 
the  same  bulk  of  MnO2.  After  putting  this  into  a  t.t.,  add  as  much 
H2SO4,  mix  them  together  by  shaking,  attach  a  d.t.,  and  conduct 
the  end  of  it  into  a  t.t.  that  is  immersed  in  a  bottle  of  cold  water. 
Slowly  heat  the  contents  of  the  t.t.,  and  notice  the  color  of  the  escap- 
ing vapor,  and  any  liquid  that  condenses  in  the  receiver.  Avoid  in- 
haling the  fumes,  or  getting  them  into  the  eyes. 

MnO2  +  2  KBr  +  2  H2SO4  =  ?  Compare  this  with  the  equation  for 
making  Cl  from  NaCl. 

158.  Tests. 

Experiment  97.  —  Try  the  bleaching  action  of  Br  vapor  as  in  the 
case  of  Cl.  Bleach  a  piece  of  litmus  paper,  and  try  to  restore  the 
color  with  NH4OH.  Explain  its  bleaching  and  disinfecting  action. 
Try  the  combustibility  of  As,  Sb,  and  Cu. 

159.  Description.  —  Bromine  at  usual  temperatures  is 
a  liquid  element ;  it  is  the  only  common  one  except  Hg ;  it 
quickly  evaporates  on  exposure  to  air.     The  chemistry  of 
its  manufacture  is  like  that  of  Cl ;  its  bleaching  and  dis- 
infecting powers  are  similar  to  the  latter,  though  they  are 
not  quite  so  strong   as   those   of   Cl.     Its  affinity  for  H 
and  for  metals  is  also  strongly  marked.     A  drop  of  Br  on 
the  skin 'produces  a  sore  slow  to  heal. 


102  BROMINE. 

Bromine  salts  are  mainly  KBr,  NaBr,  MgBr2.  These  in 
small  quantities  accompany  NaCl,  and  are  most  com- 
mon in  brine  springs.  The  world's  supply  of  Br  comes 
chiefly  from  West  Virginia  and  Ohio,  over  300,000  pounds 
being  produced  from  the  salt  (NaCl)  wells  there  in  1884. 
The  water  taken  from  these  wells  is  nearly  evaporated,  after 
which  NaCl  crystallizes  out,  leaving  a  thick  liquid  —  bit- 
tern, or  mother  liquor  —  which  contains  the  salts  of  Br. 
The  bittern  is  treated  with  H2SO4  and  MnO2,  as  above. 

For  transportation  in  large  quantities,  Br  has  to  be  made 
into  the  salts  NaBr  and  KBr,  on  account  of  the  danger 
attending  leakage  or  breakage  of  the  receptacles  for  Br. 

16O.  Uses.  —  Its  chief  uses  are  in  photography  (page 
167),  medicine,  as  KBr,  and  analytical  chemistry. 


CHAPTER   XXXII. 

IODINE. 
Examine  iodine,  potassium  iodide. 

161.  Preparation  of  I. 

Experiment  98.  —  Put  into  a  t.t.  2  or  &  of  powdered  KI  mixed 
with  an  equal  bulk  of  MnO2,  add  H2SO4  enough  to  cover  well,  shake 
together,  complete  the  apparatus  as  for  making  Br,  and  heat.  Notice 
the  color  of  the  vapor,  and  any  sublimate.  The  direct  product  of 
the  solidification  of  a  vapor  is  called  a  sublimate.  The  process  is  sub- 
limation. Observe  any  crystals  formed.  Write  the  reaction,  and  com- 
pare the  process  with  that  for  making  Br  and  Cl.  Compare  the  vapor 
density  of  I  with  that  of  Br  and  of  Cl.  With  that  of  air.  What  vapor 
is  heavier  than  I  ?  See  page  12.  What  acid  and  what  base  are  repre- 
sented by  KI  ? 

162.  Tests. 

Experiment  99.  —  (1)  Put  a  crystal  of  I  in  the  palm  of  the  hand 
and  watch  it  for  a  minute.  (2)  Put  2  or  3  crystals  into  a  t.t.,  and 
warm  it,  meanwhile  holding  a  stirring-rod  half-way  down  the  tube. 
Notice  the  vapor,  also  a  sublimate  on  the  sides  of  the  t.t.  and  rod. 
(3)  Add  to  2  or  3  crystals  in  a  t.t.  5CC  of  alcohol,  C2H5OH ;  warm  it, 
and  see  whether  a  solution  is  formed.  If  so,  add  5CC  H2O  and  look  for 
a  ppt.  of  I  Does  this  show  that  I  is  not  at  all  soluble  in  H2O,  or 
not  so  soluble  as  in  alcohol  ? 

163.  Starch  Solution  and  Iodine  Test. 

Experiment  100.  —  Pulverize  a  gram  or  two  of  starch,  put  it  into 
an  evaporating-dish,  add  4  or  5  drops  of  water,  and  mix ;  then  heat  to 
the  boiling-point  10CC  H2O  in  a  t.t.,  and  pour  it  over  the  starch,  stir- 
ring it  meanwhile. 

(1)  Dip  into  this  starch  paste  a  piece  of  paper,  hold  it  in  the  vapor 
of  I,  and  look  for  a  change  of  color.  (2)  Pour  a  drop  of  the  starch 


104  IODINE. 

paste  into  a  clean  t.t.,  and  add  a  drop  or  two  of  the  solution  of  T  in 
alcohol.  Add  5CC  H2O,  note  the  color,  then  boil,  and  finally  cool.  (3) 
The  presence  of  starch  in  a  potato  or  apple  can  be  shown  by  putting 
a  drop  of  I  solution  in  alcohol  on  a  slice  of  either,  and  observing  the 
color.  (4)  Try  to  dissolve  a  few  crystals  of  I  in  5CC  H2O  by  boiling. 
If  it  does  not  disappear,  see  whether  any  has  dissolved,  by  touching 
a  drop  of  the  water  to  starch  paste.  This  should  show  that  I  is 
slightly  soluble  in  water. 

164.  lodo-Starch  Paper. 

Experiment  101.  —  Add  to  some  starch  paste  that  contains  no  I 
5CC  of  a  solution  of  KI,  and  stir  the  mixture.  Why  is  it  not  colored 
blue  V  Dip  into  this  several  strips  of  paper,  dry  them,  and  save  for  use. 
This  paper  is  called  iodo-starch  paper,  and  is  used  as  a  test  for  ozone, 
chlorine,  etc.  Bring  a  piece  of  it  in  contact  with  the  vapor  of  chlorine, 
bromine,  or  ozone,  and  notice  the  blue  color. 

Experiment  102.  —  Add  a  few  drops  of  chlorine  water  (see  page 
98)  to  2CC  of  the  starch  and  KI  solution  in  10CC  H2O.  This  should 
show  the  same  effect  as  the  previous  experiment. 

165.  Explanation.  —  Only  free  I,  not  compounds  of  it, 
will  color  starch  blue.     It  must  first  be  set  free  from  KI. 
Ozone,  chlorine,  etc.,  have   a  strong  affinity  for    K,  and 
when  brought  in  contact  with  KI  they  unite  with  K  and 
set  free  I,  which  then  acts  on  the  starch  present.     Com- 
plete the  equation :  KI  +  Cl  =  ? 

166.  Occurrence.  —  The    ultimate  source   of   I   is  sea 
water,  of  which  it  constitutes  far  too  small  a  percentage 
to  be  separated  artificially.     Sea-weeds,  or  algae,  especially 
those  growing  in  the  deep  sea,  absorb  its  salts  —  Nal,  KI, 
etc.  —  from  the  water.     It  thus  forms  a  part  of  the  plant, 
and  from  this  much  of  the  I  of  commerce  is  obtained.   Algse 
are  collected  in  the  spring,  on  the  coasts  of  Ireland,  Scot- 
land, arid  Normandy,  where  rough  weather  throws  them 
up.     They  are  dried,  and  finally  burned  or  distilled ;  the 


IODINE.  105 

ashes  are  leached  to  dissolve  I  salts ;  the  water  is  nearly 
evaporated,  and  the  residue  is  treated  with  H2SO4  and 
MnO2,  as  in  the  case  of  Br  and  Cl.  I  also  occurs  in  Chili, 
as  Nal  and  NaIO3,  mixed  with  NaNO3.  This  is  an  impor- 
tant source  of  the  I  supply. 

167.  Uses.  —  I  is  much  used  in  medicine,  and  was  for- 
merly employed  in  taking  daguerreotypes  and  photographs. 
Its  solution  in  alcohol  or  in  ether  is  known  as  tincture  of 
iodine. 

168.  Fluorine.  —  F,  Cl,  Br,  I,  are  called  halogens  or  haloids,  and 
exist  in  compounds  —  salts  —  in  sea  water.     F  is  the  most  active  of  all  ele- 
ments, combining  with  every  element  except  O.     Until  recently  it  has  never 
been  isolated,  for  as  soon  as  set  free  from  one  compound  it  attacks  the  near- 
est substance,  and  seems  to  be  as  much  averse  to  combining  with  itself,  or 
to  existing  in  the  elementary  state,  as  to  uniting  with  0.     It  is  supposed  to 
be  a  gas,  and,  as  is  claimed,  has  lately  been  isolated  by  electrolysis  from 
HF  in  a  Pt  U-tube.     Fluorite  (CaF2)  and  cryolite  (A12F6  +  6  NaF)  are 
its  two  principal  mineral  sources.     The  enamel  of  the  teeth  contains  F  in 
composition. 


CHAPTER    XXXIII. 
THE   HALOGENS. 

169.  Halogens  Compared.  —  The  elements  F,  Cl,  Br, 
I,  form  a  natural  group.  Their  properties,  as  well  as  those 
of  their  compounds,  vary  in  a  step-by-step  way,  as  seen 
below.  F  is  sometimes  an  exception.  They  are  best  re- 
membered by  comparing  them  with  one  another.  Notice  : 

1.  Similarity  of  name-ending.     Each  name  ends  in  ine. 

2.  Similarity   of    origin.      Salt   water   is   the    ultimate 
source  of  all,  except  F. 

8.  Similarity  of  valence.     Each  is  usually  a  monad. 

4.  Similarity   of  preparation.      Cl,  Br,  I,  are   obtained 
from  their  salts  by  means  of  MnO2  and  H2SO4. 

5.  Variation  in  occurrence.      Cl  occurs  in  sea-salt,  Br 
in  sea-water,  I  in  sea-weed. 

6.  Variation  in  color;  F  being  colorless,  Cl  green,  Br 
red,  I  violet. 

7.  Gradation  in  sp.  gr. ;  F  19,  Cl  35.5,  Br  80,  I  127. 

8.  Gradation  in  state,  corresponding  to  sp.  gr. ;  F  being 
a  light  gas,  Cl  a  heavy  gas,  Br  a  liquid,  I  a  solid. 

9.  Corresponding  gradation  in  their  usual  chemical  ac- 
tivity ;  F  being  most  active,  then  Cl,  Br,  and  I. 

10.  Corresponding  gradation  in  the  strength  of  the    H 
acids ;  the  strongest  being  HF,  the  next,  HC1,  etc. 

11.  Corresponding  gradation  in  the  explosibility  of  their 
N  compounds ;  the  strongest  NC13,  the  next,  NBrs,  etc. 

12.  Corresponding  gradation  in  the  number  of  H  and 
O  acids ;  Cl  4,  Br  3,  I  2. 


THE   HALOGENS. 


10: 


1 7O.    Compounds.  —  The  following  are  some  of  the  oxides,  acids, 
and  salts  of  the  halogens.     Name  them. 

C120    (+H2O  =  )  2  HC1O.    The  salts  are  hypochlorites,  as  Ca(C10)2. 
The  salts  are  chlorites,  as  KC1O2. 


C12O3  (+H2O  =  )  2HC1O2. 
C1204. 

HC103. 
HC104. 


The  salts  are  chlorates,  as  KC103. 
The  salts  are  perchlorates,  as  KC104. 


I205(+H20=)       2HI03 


HBrO.  The  salts  are       ?  KBrO. 

The  salts  are  wanting. 

HBr03.  The  salts  are       ?  KBrO3. 

HBr04.  The  salts  are       ?  KBr04. 


The  salts  are  wanting-. 

The  salts  are  wanting. 

The  salts  are        ?  KI03. 

The  salts  are        ?  KI04. 


F  forms  no  oxides,  and  no  acids  except  HF.  HF,  HC1,  HBr,  HI,  are 
striking  illustrations  of  acids  with  no  O.  HC104  is  a  very  strong  oxidizing 
agent.  A  drop  of  it  will  set  paper  on  fire,  or  with  powdered  charcoal  ex- 
plode violently.  This  is  owing  to  the  ease  with  which  it  gives  up  0.  Notice 
why  its  molecule  is  broken  up  more  readily  than  HC1O3.  The  higher  the 
molecular  tower,  or  the  more  atoms  it  contains,  the  greater  its  liability  to 
fall.  Some  organic  compounds  contain  hundreds  of  atoms,  and  hence  are 
easily  broken  down,  or,  as  we  say,  are  unstable.  Inorganic  compounds  are, 
as  a  rule,  much  more  stable  than  organic  ones.  It  is  not  always  true,  how- 
ever, that  the  compound  with  the  least  number  of  atoms  is  the  most  stable. 
S02  is  more  stable  than  S03,  but  H2SO3  is  less  so  than  H2SOA. 


CHAPTER   XXXIV. 

VAPOR   DENSITY  AND  MOLECULAR    WEIGHT. 

Examine  a  liter  measure,  in  the  form  of  a  cube,  —  cubic  decimeter, 
—  and  a  cubic  centimeter. 

171.  Gaseous  Weights  and  Volumes.  —  A  liter  of  H, 
at  0°  and  760mm,  weighs  nearly  0.09g.     This  weight  is  called 
a  crith.     Find  the  weight  of  H  in  the  following,  in  criths 
and  in  grams :  151,  0.071,  50.31,  0.0351,  0.61. 

It  has  been  estimated  that  there  are  (10)24  molecules  of 
H  in  a  liter.  Does  the  number  vary  for  different  gases  ? 
The  weight  of  a  molecule  of  H  in  parts  of  a  crith  is 
-^1^,  5  in  parts  of  a  grain  -r~t.  If  the  H  molecule  is  com- 
posed of  2  atoms,  what  is  the  weight  of  its  atom  in  frac- 
tions of  a  crith?  What  in  fractions  of  a  gram?  The 
weight  of  the  H  atom  is  a  microcrith.  What  part  of  a 
crith  is  a  microcrith? 

172.  Vapor  Density.  —  Vapor  density,  or  specific  grav- 
ity referred  to  H  as  "the  standard   (Physics,  page  59),  is 
the  ratio  of  the  weight  of  a  given  volume  of  a  gas  or  vapor 
to  the  weight  of  the  same  volume  of  H.     A  liter  of  steam 
weighs  nine  times  as  much  as  a  liter  of  H.     Its  vapor  den- 
sity is  therefore  nine.     For  convenience,  a  definite  volume 
of  H  is  usually  taken  as  the  standard,  viz.,  the  H  atom.    The 
volume  of  the  H  atom  and  that  of  the  half-molecule  of 
H2O,  or  of  any  gas  are  identical,  each  being  represented 
by  one  square,  D-     If?  then,  the  standard  of  vapor  density 
is  the  H  atom,  half  the  molecular  weight  of  a  gas  must  be 


> 
VAPOR   DENSITY   AND   MOLECULAR   WEIGHT.          109 

its  vapor  density,  since  it  is  evident  that  we  thus  compare 
the  weights  of  equal  volumes.  The  vapor  density  of  H2O, 
steam,  is  found  from  the  symbol  as  follows  :  (2  +  16)  •+•  2 
=  9.  To  obtain  the  vapor  density  of  any  compound  from 
the  formula,  we  have  only  to  divide  its  molecular  weight 
by  two.  Find  the  vapor  density  of  HC1,  N2O,  NO, 
Ci2H22Ou,  Cl,  CO2,  HF,  SO2.  Explain  each  case. 

The  half-molecule,  instead  of  the  whole,  is  taken,  be- 
cause our  standard  is  the  hydrogen  atom  D,  the  smallest 
portion  of  matter,  by  weight,  known  to  science. 

How  many  criths  in  a  liter  of  HC1  ?  How  many  grains  ? 
Compute  the  number  of  criths  and  of  grams  in  one  liter  of 
the  compounds  whose  symbols  appear  above. 

PROBLEMS. 

(1)  A  certain  volume  of  H  weighs  0.36s  at  standard  temperature 
and  pressure.     How  many  liters  does  it  contain  ?     If  one  liter  weighs 
0.098,  to  weigh  0.36*  it  will  take  0.36  +  0.09  =  4  liters. 

(2)  How  many  liters,  or  criths,  of  H  in  63«?     2.7*?      IK?     5«? 
250e  ?    Explain  each. 

(3)  Suppose  the  gas  to  be  twice  as  heavy  as  H,  how  many  liters  in 
0.36g?     A  liter  of  the  gas  will  weigh  0.18*  (0.09  X  2).     In  0.36&  there 
will  be  0.36  +0.18  =  2.     Answer  the  question  for  63&,  2.7*,  etc. 

(4)  How  many  liters  of  Cl  in  each  of  the  above  numbers  of  grams? 

(5)  How  many  of   HC1?     H2O  (steam)?      CO2?      Explain  fully 
every  case. 

Vapor  density  is  very  easily  determined  from  the  for- 
mula by  the  method  given  above.  But  in  practice  the  for- 
mula is  obtained  from  the  vapor  density,  and  hence  the 
method  there  given  has  to  be  reversed. 

173.  Vapor  Density  of  Oxygen.  —  Suppose  we  were 
to  obtain  the  vapor  density  of  O.  We  should  carefully 
seal  and  weigh  a  given  volume,  say  a  liter,  at  a  noted 
temperature  and  barometric  pressure,  which  are  reduced 


110          VAPOR   DENSITY   AND   MOLECULAR   WEIGHT. 

to  0°  and  760mm,  and  compare  it  with  the  weight  of  the  same 
volume  of  H.  This  has  been  done  repeatedly,  and  O  has 
been  found  to  weigh  16  times  as  much  as  H,  volume  for 
volume,  or,  more  exactly,  15.96+.  Now  a  liter  of  each  gas 
has  the  same  number  of  molecules,  therefore  the  O  mole- 
cule weighs  16  times  the  H  molecule.  The  half-molecule 
of  each  has  the  same  proportion,  and  the  vapor  density  of 
O  is  16.  Atomic  weight  is  obtained  in  a  very  different  way. 

PROBLEMS. 

(1)  A  liter  of  Cl  is  found  to  weigh  3.195s.      Compute  its  vapor 
density,  and  explain  fully. 

(2)  A  liter  of  Hg  vapor,   under  standard  conditions,  weighs  9s. 
Find  its  vapor  density,  and  explain. 

The  vapor  density  of  only  a  few  elements  has  been  satisfactorily  deter- 
mined. See  page  12.  Some  cannot  be  vaporized ;  others  can  be,  but  only 
under  conditions  which  prevent  weighing  them.  The  vapor  density  of 
very  many  compounds  also  is  unknown. 

(3)  A  liter  of  CO2  weighs  1.98s.     Find  the  vapor  density,  and  from 
that  the  molecular  weight,  remembering  that  the  latter  is  twice  the  for- 
mer. See  whether  it  corresponds  to  that  obtained  from  the  formula,  CO2. 
This  is,  in  fact,  the  way  a  formula  is  ascertained,  if  the  atomic  weights 
of  its  elements  are  known. 

(4)  A  liter  of  a  compound  gas  weighs  2.88s.     Analysis  shows  that 
its  weight  is  half  S  and  half  O.     As  the  atomic  weight  of  S  is  32,  and 
that  of  O  is  16,  what  is  the  symbol  for  the  gas? 

Solution.  Its  molecular  weight  is  64,  i.e.  (2.88 -r-  0.09)  X  2,  of  which 
32  is  S  and  32  O.  The  atomic  weight  of  S  is  32,  hence  there  is  one 
atom  of  S,  while  of  O  there  are  two  atoms.  The  formula  is  SO2. 

(5)  A  liter  of  a  compound  gas,  which  is  found  to  contain  f  C  and 
f  O  by  weight,  weighs  1.26s.     What  is  its  formula?    Atomic  weights 
are  taken  from  page  12.     Prove  your  answer. 

(6)  A  liter  of  a  compound  of  N  and  O  weighs  1.98«.     The  N  is  TV 
and  the  O  T4T.     What  is  the  gas  ? 

(7)  A  compound  of  N  and  H  gas  weighs  0.765s  to  the  liter.     The 
N  is  ]4  of  the  whole,  the  H  TV     What  gas  is  it? 


CHAPTER   XXXV. 

ATOMIC    WEIGHT. 

1 74.  Definition.  —  We  have  seen  that  the   molecular 
weight  of  a  compound,  as  well  as  of  most  elements,  is  ob- 
tained from  the  vapor  density  by  doubling  the  latter.     It 
remains  to  explain  how  atomic  weights  are  obtained.    The 
term  is  rather  misleading.     The  atomic  weight  of  an  ele- 
ment is  its  least  combining  weight,  the  smallest  portion  that 
enters  into  chemical  union,  which  is,  of  course,  the  weight 
of  an  atom. 

175.  Atomic  Weight  of  Oxygen.  —  Suppose  we  wish  to 
find  the  atomic  weight  of   oxygen.     We  must   find   the 
smallest  proportion  by  weight  in  which  it  occurs  in  any 
compound.     This  can  only  be  done  by  analyzing  all  the 
compounds  of  O  that  can  be  vaporized.     As  illustrative  of 
these  compounds  take  the  six  following:  — 

Wt.  of  other 
Names.  V.d.          Mol.  wt.      Wt.  of  O.        Elem.         Symbol. 

Carbon  monoxide      .     .     .  14  28  16  12  ? 

Carbon  dioxide      ....  22  44  32  12  ? 

Hydrogen  monoxide ...  9  18  16  2  ? 

Nitrogen  monoxide    ...  22  44  16  28  ? 

Nitrogen  trioxide    .  .     ,,  .  38  76  48  28  ? 

Nitrogen  pentoxide    ...  54  108  80  28  ? 

176.  Molecular  Symbols.  —  From  the  vapor  density  of 
the  gases  —  column  2 — we  obtain  their  molecular  weight — 
column  3.     To  find  the  proportion  of  O,  it  must  be  separa- 


112  ATOMIC    WEIGHT. 

ted  by  chemical  means  from  its  compounds  and  separately 
weighed.  These  relative  weights  are  given  in  column  4. 
Now  the  smallest  weight  of  O  which  unites  in  any  case  is  its 
atomic  weight.  If  any  compound  of  O  should  in  future  be 
found  in  which  its  combining  weight  is  8  or  4,  that  would 
be  called  its  atomic  weight.  By  dividing  the  numbers  in 
column  4,  wt.  of  O,  by  16,  the  atomic  weight  of  O,  we  ob- 
tain the  number  of  O  atoms  in  the  molecule.  Subtracting 
the  weights  of  O  from  the  molecular  weights,  we  have  the 
parts  of  the  other  elements,  column  5,  and  dividing  these 
by  the  atomic  weight  of  the  respective  elements,  we  have 
the  number  of  atoms  of  those  elements ;  these  last,  com- 
bined with  the  number  of  O  atoms,  give  the  symbol.  In 
this  way  complete  the  last  column. 

Show  how  to  get  the  atomic  rveight  of  Cl  from  -these  compounds, 
arranging  them  in  tabular  form,  and  completing  as  above:  HC1,  KC1, 
NaCl,  ZnCl2,  MgCl2 ;  the  atomic  weight  of  N  in  these  :  N2O,  NO,  NH3. 

177.  Molecular  and  Atomic  Volumes.  —  We  thus  see 
that  vapor  density  and  atomic  weight  are  obtained  in  two 
quite  different  ways.  In  the  case  of  elements  the  two  are 
usually  identical,  i.e.  with  the  fe-w  whose  vapor  density  is 
known ;  but  this  is  not  always  true,  and  it  leads  to  inter- 
esting conclusions  regarding  atomic  volume.  In  O  both 
vapor  density  and  atomic  weight  are  16.  This  gives  2 
atoms  of  O  to  the  molecule,  i.e.  the  molecular  weight  -r- 
the  atomic  weight.  The  size  of  an  O  atom  is  therefore 
half  the  gaseous  molecule,  and  is  represented  by  one  square, 
Q  S  has  a  vapor  density  arid  an  atomic  weight  of  32  each. 
Compute  the  number  of  atoms  in  the  molecule.  Compute 
for  I,  in  which  the  two  are  identical,  127.  P  has  an  atomic 
weight  of  31,  while  its  vapor  density  is  62.  Its  molecule 
must  consist  of  4  atoms,  each  half  the  size  of  the  H  atom, 


ATOMIC   WEIGHT.  113 

D.  The  vapor  density  of  As  is  150,  the  atomic  weight 
75.  Compute  the  number  of  atoms  in  its  molecule,  and 
represent  their  relative  size.  Hg  has  an  atomic  weight  of 
200,  a  vapor  density  of  100.  Compute  as  before,  and  com- 
pare the  results  with  those  on  page  12.  Ozone  has  an 
atomic  weight  of  16,  a  vapor  density  24.  Compute. 


CHAPTER   XXXVI. 
DIFFUSION  AND   CONDENSATION  OF  GASES. 

178.  Diffusion  of  Gases.  —  Oxygen  is  16  times  as  heavy 
as  H.     If  the  two  gases  were  mixed,  without  combining, 
in  a  confined  space,  it  might  be  supposed  that  O  would 
settle  to  the  bottom  and  H  rise  to  the  top.    This  would,  in 
fact,  take  place  at  first,  but  only  for  an  instant,  for  all  gases 
tend  to  diffuse  or  become  intimately  mixed.     The  lighter 
the  gas  the  more  quickly  it  diffuses. 

179.  Law  of  Diffusion  of  Gases.  —  The  diffusibility  of 
gases  varies  inversely  as  the  square  roots  of  their  vapor  densi- 
ties.    Compare  the  diffusibility  of  H  with  that  of  O. 

dif.  H  >  dif.  0  :  :  Vl6  :  Vl,  or  dif.  H  r  dif.  O  : :  4  :  1. 

That  is  to  say,  if  H  and  O  be  set  free  from  separate  re- 
ceivers in  a  room,  the  H  will  become  intermingled  with  the 
atmosphere  four  times  as  quickly  as  the  O.  Compare  the 
diffusibility  of  O  and  N ;  of  Cl  and  H.  Take  the  atomic 
weights  of  these,  since  they  are  the  same  as  the  vapor 
densities.  In  case  of  a  compound  gas,  half  the  molecular 
weight  must  be  taken  for  the  vapor  density;  e.g. 

dif.  N2O  :  dif.  0  : :  Vl6  :  \/22. 

180.  Cause.  —  Diffusion  is  due  to  molecular  motion;  the  lighter 
the  gas  the  more  rapid  the  vibration  of  its  molecules.     Compare  the  diffu- 
sibility of  CO2  and  that  of  Cl ;  of  HC1  and  SO2 ;  of  HF  and  I. 


DIFFUSION    AND    CONDENSATION.  115 

181.  Liquefaction  and  Solidification  of  Gases.  —  Wa- 
ter boils  at  100°,  under  standard  pressure,  though  evapo- 
rating at  all  temperatures ;  it  vaporizes  at  a  lower  point  if 
the  pressure  be  less,  as  on  a  mountain,  and  at  a  higher 
temperature  if  the  pressure  be  greater,  as  at  points 
below  the  sea  level.  Alcohol  boils  at  78°,  standard  pres- 
sure, and  every  liquid  has  a  point  of  temperature  and 
pressure  above  which  it  must  pass  into  the  gaseous  state. 
Likewise  every  gas  has  a  critical  temperature  above  which 
it  cannot  be  liquefied  at  any  pressure. 

This  condition  was  not  recognized  formerly,  and  before 
1877,  O,  H,  N,  CH4,  CO,  NO,  etc.,  had  not  been  liquefied, 
though  put  under  a  pressure  of  more  than  2,000  atmos- 
pheres. They  were  called  permanent  gases.  In.  1877 
Cailletet  and  Pictet  liquefied  and  solidified  these  and 
others.  The  lowest  temperature,  about— 225°,  was  pro- 
duced by  suddenly  releasing  the  pressure  from  solid  N  to 
4mm,  which  caused  it  rapidly  to  evaporate.  Evaporation, 
especially  under  diminished  pressure,  always  lowers  the 
temperature  by  withdrawing  heat. 

These  low  degrees  are  indicated  by  a  H  thermometer, 
or  if  too  low  for  that,  by  a  "  thermo-electric  couple  "  of 
copper  and  German  silver. 

The  pupil  can  easily  liquefy  S02  by  passing  it  through  a  U-tube  which 
is  surrounded  by  a  mixture  of  ice  and  salt  in  a  large  receiver.  At  the 
meeting  of  the  American  Association  for  the  Advancement  of  Science 
in  1887,  a  solid  brick  of  CO2  was  seen  and  handled  by  the  members. 
Liquid  H  is  steel  blue. 

A  few  results  obtained  under  a  pressure  of  one  atmosphere  are :  — 

Boiling  Points :  C2H4-102°;  CH4-184°;  0-181°;  N-1940;  CO- 
190°;  NO -154°;  Air -191°. 

Solidifying  Points:  01-102°;  HC1-1150;  Ether -129°;  Alcohol - 
130°. 


CHAPTER   XXXVII. 
SULPHUR. 

Examine  brimstone,  flowers  of  sulphur,  pyrite,  chalcopyrite,  spha- 
lerite, galenite,  gypsum,  barite. 

182.  Separation. 

Experiment  103.  —  To  a  solution  of  2s  of  sodium  sulphide,  Na.2S.2, 
in  10CC  H2O  add  3  or  4CC  HC1,  and  look  for  a  ppt.  Filter,  and  examine 
the  residue.  It  is  lac  sulphur,  or  milk  of  sulphur. 

183.  Crystals  from  Fusion. 

Experiment  104.  — In  a  beaker  of   25  or  50CC  capacity  put  20« 
brimstone.     Place  this  over  a  flame  with  asbestus  paper  interposed, 
and  melt  it  sloivly.     Note  the  color  of  the  liquid, 
then  let  it  cool,  watching  for  crystals.    When  part- 
ly solidified  pour  the  liquid  portion  into  an  evapo- 
rating-dish  of  water,  and  observe  the  crystals  of  S 
forming  in  the  beaker  (Fig.  42).     The  hard  mass 
may  be  separated  from  the  glass  by  a  little  HNOS 
Fig.  42.          an^  a  *kin  knife-blade,  or  by  CS2. 

184.  Allotropy. 

Experiment  105.  —  Place  in  a  t.t.  15^  of  brimstone,  then  heat 
slowly  till  it  melts.  Notice  the  thin  amber-colored  liquid.  The  tem- 
perature is  now  a  little  above  100°.  As  the  heat  increases,  notice  that  it 
grows  darker  till  it  becomes  black  and  so  viscid  that  it  cannot  be  poured 
out.  It  is  now  above  200°.  Still  heat,  and  observe  that  it  changes  to 
a  slightly  lighter  color,  and  is  again  a  thin  liquid.  At  this  time  it  is 
above  300°.  Now  pour  a  little  into  an  evaporating  dish  containing 
water.  Examine  this,  noticing  that  it  can  be  stretched  like  rubber. 
Leave  it  in  the  water  till  it  becomes  hard.  Continue  heating  the 


SULPHTTR.  117 

brimstone  in  the  t.t.  till  it  boils  at  about  450°,  and  note  the  color  of 
the  escaping  vapor.  Just  above  this  point  it  takes  fire.  Cool  the  t.t., 
holding  it  in  the  light  meantime,  and  look  for  a  sublimate  of  S  on  the 
sides. 

185.  Solution. 

Experiment  106.  —  Place  in  an  evaporating-dish  a  gram  of  pow- 
dered brimstone,  and  add  5CC  CS2,  carbon  disulphide.  Stir,  and  see 
whether  S  is  dissolved.  Put  this  in  a  draft  of  air,  and  note  the  evapo- 
ration of  the  liquid  CS2  and  the  deposit  of  S  crystals.  These  crystals 
are  different  in  form  from  those  resulting  from  cooling  from  fusion. 

186.  Theory  of  Allotropy. — The  last  three  experiments 
well  illustrate  allotropy.     .We  found  S  to  crystallize  in 
two  different  ways.     Substances  can  crystallize  in  seven 
different  systems,  and  usually  a  given  substance  is  found 
in  one  of   these  systems  only ;    e.g.  galena   is  invariably 
cubical.      An    element  having  two  such  forms  is  said  to 
be  dimorphous.      If  it  crystallizes  in  three  systems,  it  is 
trimorphous.     A  crystal  has  a  definite  arrangement  of  its 
molecules.     If   without   crystalline    form,  a  substance    is 
called  amorphous.    An  illustration  of  amorphism  was  S  after 
it  had  been  poured  into  water.     Thus  S  has  at  least  three 
allotropic  forms,  and  the  gradations  between  these  probably 
represent   others.      Allotropy  seems  to  be  due  to  varied 
molecular  structure.    We  know  but  little  of  the  molecular 
condition  of  solids  and  liquids,  since  we  have  no  law  to 
guide  us  like  Avogadro's  in  gases ;  but,  from  the  density 
of  S  vapor  at  different  temperatures,  we  infer  that  liquids 
and  solids  have  their  molecules  very  differently  made  up 
from  those  of  gases.     The  least  combining  weight  of  S  is 
32.     Its  vapor  density  at  1,000°  is  32;  hence  its  molecular 
weight  is  64,  i.e.  vapor  density  X  2 ;  and  there  are  2  atoms 
in  its  molecule  at  that  temperature,  molecular  weight  -*- 
atomic  weight.     At  500°,  however,  the  vapor  density  is  96 


118 


SULPHUR. 


and  the  molecular  weight  192.  At  this  degree  the  molecule 
must  contain  6  atoms.  How  many  it  has  in  the  allotropic 
forms,  as  a  solid,  is  beyond  our  knowledge  ;  but  it  seems 
quite  likely  that  allotropy  is  due  to  some  change  of 
molecular  structure. 

The  above  experiments  show  two  modes  of  obtaining  crystals,  by  fusion 
and  by  solution. 

187.  Occurrence  and  Purification.  —  Sulphur  occurs 
both  free  and  combined,  and  is  a  very  common  element. 
It  is  found  free  in  all  volcanic  regions,  but  Sicily  furnishes 
most  of  it.  Great  quantities  are  thrown  up  from  the  inte- 
rior of  the  earth  during  an  eruption.  The  heat  of  volcanic 
action  probably  separates  it  from  its  compound,  which  may 
be  CaSO4.  Vast  quantities  of  the  poisonous  SO2  gas  are  also 
liberated  during  an  eruption,  this  being,  in  volume  of  gases 

evolved,  next  to  H2O. 
S  is  crudely  separated 
from  its  earthy  impuri- 
ties in  Sicily  by  piling 
it  into  heaps,  covering 
to  prevent  access  of 
air,  and  igniting,  when 
some  of  the  S  burns, 
and  the  rest  melts  and 
is  collected.  After  re- 
moval from  the  island 
it  is  further  purified 
by  distilling  in  retorts 
connected  with  large  chambers  where  it  sublimes  on  the 
sides  as  flowers  of  sulphur  (Fig.  43).  This  is  melted  and 
run  into  molds,  forming  roll  brimstone.  S  also  occurs  as  a 
constituent  of  animal  and  vegetable  compounds,  as  in  inus- 


Fig.  43. 


SULPHURo  119 

tard,  hair,  eggs,  etc.  The  tarnishing  of  silver  spoons  by 
eggs  is  due  to  the  formation  of  silver  sulphide,  Ag2S. 
The  yellow  color  of  eggs,  however,  is  due  to  oils,  not  to  S. 

The  main  compounds  of  S  are  sulphides  and  sulphates.  What  acids  do 
they  respectively  represent  1  Metallic  sulphides  are  as  common  as  oxides ; 
e.g.  FeS2,  or  pyrite,  PbS,  or  galenite,  ZnS,  or  sphalerite,  CuFeS2,  or  chal- 
copyrite,  etc.  The  most  abundant  sulphate  is  CaS04,  or  gypsum.  BaSO4, 
or  barite,  and  Na2S04,  or  Glauber's  salt,  are  others. 

The  only  one  of  these  compounds  that  is  utilized  for  its  S  is  FeS2.  In 
Europe  this  furnishes  a  great  deal  of  the  S  for  H2SO4.  S  is  obtained  by 
roasting  FeS2.  3  FeS2  =  Fe3S4  +  2  S. 

188.  Uses.  —  The  greatest  use  of  S  is  in  the  manufac- 
ture of  H2SO4.    A  great  deal  is  used  in  making  gunpowder, 
matches,  vulcanized  rubber,  and  the  artificial    sulphides, 
like  HgS,  H2S,  CS2,  etc.     The  last  is  a  very  volatile,  ill- 
smelling  liquid,  made  by  the  combination  of  two  solids, 
S  being  passed  over  red-hot  charcoal.     It  dissolves  S,  P, 
rubber,  gums,  and  many  other  substances  insoluble  in  H2O. 

189.  Sulphur  Dioxide,  SO2,  has  been   made   in   many 
experiments.     It  is  a  bleaching  agent,  a  disinfectant,  and 
a  veiy  active  compound,  having  great  affinity  for  water, 
but  it  will  not  support  combustion.     Like  most  disinfec- 
tants, it  is  very  injurious  to  the  system.      It  is  used  to 
bleach   silk   and  wool  —  animal   substances  —  and   straw 
goods,  which  Cl  would  injure;   but  the  color  can  be  re- 
stored, as  the  coloring  molecule  seems  not  to  be  broken 
up,  but  to  combine  with  SO2,  which  is  again  separated  by 
reagents.      Goods   bleached   with   SO2  often  turn  yellow 
after  a  time. 

190.  SO2  a  Bleacher. 

Experiment  107.  —  Test  its  bleaching  power  by  burning  S  under 
a  receiver  under  which  a  wet  rose  or  a  green  leaf  is  also  placed. 


CHAPTER   XXXVIII. 

HYDROGEN  SULPHIDE. 
Examine  ferrous  sulphide,  natural  and  artificial. 

191.  Preparation. 

Experiment  108.  —  Put  a  gram  of  ferrous  sulphide  (FeS)  into  a 
t.t.  fitted  with  a  d.t.,  as  in  Figure  32.  Add  10CC  H2O  and  5CC  H2SO4. 
H2S  is  formed.  Write  the  equation,  omitting  H2O.  What  is  left  in 
solution  ? 

192.  Tests. 

Experiment  109.  —  (1)  Take  the  odor  of  the  escaping  gas.  (2) 
Pour  into  a  t.t.  5CC  solution  AgNO3,  and  place  the  end  of  the  d.t.  from 
a  H2S  generator  into  the  solution  and  note  the  color  of  the  ppt.  What 
is  the  ppt.  ?  Write  the  equation.  (3)  Experiment  in  the  same  way 
with  Pb(NO3)2  solution.  Write  the  equation.  (4)  Let  some  H2S 
bubble  into  a  t.t.  of  clean  water.  To  see  whether  H2S  is  soluble  in 
H2O,  put  a  few  drops  of  the  water  on  a  silver  coin.  Ag2S  is  formed. 
Describe,  and  write  the  equation.  Do  the  same  with  a  copper  coin. 
(5)  Put  a  drop  of  lead  acetate  solution,  Pb(C2H3O2)2,  on  a  piece  of 
unglazed  paper,  and  hold  this  before  the  d.t.  from  which  H2S  is  escap- 
ing. PbS  is  formed.  Write  the  equation.  This  is  the  characteristic 
test  of  H2S. 

193.  Combustion  of  H2S. 

Experiment  110.  —  Attach  a  philosopher's  lamp  tube  to  the  H2S 
generator,  and,  observing  the  same  precautions  as  with  H,  light  the 
gas.  What  two  products  must  be  formed  ?  State  the  reaction.  The 
color  of  the  flame.  Compute  the  molecular  weight  and  the  vapor 
density  of  H2S. 


HYDROGEN   SULPHIDE.  121 

194.  Uses.  —  Hydrogen  sulphide    or  sulphuretted  hy- 
drogen, H2S,  is  employed  chiefly  as  a  reagent  in  the  chem- 
ical  laboratory.     It   forms    sulphides  with   many  of   the 
metals,  as  shown  in  the  last  experiment.     These  are  pre- 
cipitated from  solution,  and  may  be  separated  from  other 
metals  which  are  not  so  precipitated,  as  was  found  in  the 
case  of  HC1  and  NH4OH.     The-  subjoined  experiment  will 
illustrate  this.     Suppose  we  wished  to  separate  Pb  from 
Ba,  having  salts  of  the  two  mixed  together,  as  Pb(NO3)2 
and  Ba(NO3)2. 

195.  H2S  an  Analyzer  of  Metals. 

Experiment  111.  —  Pass  some  H2S  gas  into  5CC  solution  Ba(NO3)2. 
No  ppt.  is  formed.  Do  the  same*with  Pb(NO3)2  solution.  A  ppt. 
appears.  Now  mix  5CC  of  each  of  these  solutions  in  a  t.t.,  and  pass 
the  gas  from  a  H2S  generator  into  the  liquid.  What  is  precipitated,  and 
what  is  unchanged  ?  When  fully  saturated  with  the  gas,  as  indicated 
by  the  smell,  filter.  Which  metal  is  on  the  filter  and  which  is  in 
the  filtrate?  Other  reagents,  as  Na2C()3  solution,  would  precipitate 
the  latter. 

196.  Occurrence  and  Properties.  —  H2S  is  an  ill-smell- 
ing, poisonous  gas,  formed  in  sewers,  rotten  eggs,  and  other 
decaying  albuminous  matter.     It  is  formed  in  the  earth, 
probably  from  the  aqtion  of  water  on  sulphides,  and  issues 
with  water  from  sulphur  springs. 

« 

A  characteristic  property  is  the  formation  of  metallic  sulphides,  as 
above.  A  skipper  one  night  anchored  his  newly  painted  vessel  near  the 
Boston  gas-house,  where  the  refuse  was  deposited,  with  its  escaping  H2S. 
In  the  morning,  to  his  consternation,  the  craft  was  found  to  be  black. 
H2S  had  come  in  contact  with  the  lead  in  the  white  paint,  forming  black 
PbS.  This  gradually  oxidized  after  reaching  the  open  sea,  and  the  white 
color  reappeared. 


CHAPTER   XXXIX. 

PHOSPHORUS. 

NOTE.  —  Phosphorus  should  be  kept  in  water,  and  handled  with 
forceps,  never  with  the  fingers,  except  under  water,  as  it  is  liable  to 
burn  the  flesh  and  produce  ulcerating  sores.  Pieces  not  larger  than 
half  a  pea  should  be  used,  and  every  bit  should  finally  be  burned. 

197.  Solution  and  Combustion. 

Experiment  112.  —  Put  1  or  .2  pieces  of  P  into  an  evaporating- 
dish,  and  pour  over  them  5  or  10CC  CS2  —  carbon  disulphide.  This 
will  be  enough  for  a  class.  When  dissolved,  dip  pieces  of  unglazed 
paper  into  it,  and  hold  these  in  the  air,  looking  for  any  combustion 
as  they  dry.  The  P  is  finely  divided  in  solution,  which  accounts  for 
its  more  ready  combustion  then.  Notice  that  the  paper  is  not  de- 
stroyed. This  is  an  example  of  so-called  "  spontaneous  combustion." 
The  burning-point  of  P,  the  combustible,  in  air,  the  supporter,  is 
about  60°. 

198.  Combustion  under  Water. 

Experiment  113.  —  Put  a  piece  of  P  in  a  t.t.  which  rests  in  a 
receiver,  add  a  few  crystals  KC1O3  and  5CC  H2O.  Now  pour  in  through 
a  thistle-tube  lcc  or  more  of  H2SO4.  Look  for  any  flame.  1T.2SO4 
acts  very  strongly  on  KC1O3.  What  is  set  free?  From  this  fact 
explain  the  combustion  in  water. 

199.  Occurrence.  —  P  is  very  widely  disseminated,  but 
not  abundant,  and  is  found  only  in  compounds,  the  chief 
of  which  is  calcium  phosphate    Ca3(PO4)2.     It  occurs  in 
granite  arid  other  rocks,  as  the  mineral  apatite,  in  soils,  in 
plants,  particularly  in  seeds  and  grains,  and  in  the  bones, 
brains,  etc.,  of  vertebrates.     From  the  human  system  it  is 
excreted  by  the  kidneys  as  microcosmic  salt,  HNaNH4P(X; 


PHOSPHORUS.  123 

and  when  the  brain  is  hard-worked,  more  than  usual  is 
excreted.  Hence  brain-workers  have  been  said  to  "  burn 
phosphorus." 

200.  Sources.  —  Rocks  are  the  ultimate  source  of  this 
element.     These,  by  the   action  of  heat,  rain,  and  frost, 
are  disintegrated  and  go  to  make  soils.     The  rootlets  of 
plants  are  sent  through  the  soil,  and,  among  other  things, 
soluble  phosphates  in  the  earth  are  absorbed,  circulated 
by  the  sap,  and  selected  by  the  various  tissues.     Animals 
feed  on  plants,  and  the  phosphates  are  circulated  through 
the  blood,  and  deposited  in  the  osseous  tissue,  or  wherever 
needed. 

Human  bones  contain  nearly  60  per  cent  of  Ca3(PO4)2 ; 
those  of  some  birds  over  80  per  cent. 

The  main  sources  of  phosphates  and  P  are  the  phosphate 
beds  of  South  Carolina,  the  apatite  beds  of  Canada,  and 
the  bones  of  animals. 

201 .  Preparation   of  Phosphates  and  Phosphorus.  — 

Bone  ash,  obtained  by  burning  or  distilling  bones,  and  grinding  the  res- 
idue, is  treated  with  H2S04,  and  forms  soluble  H4Ca(PO4)2,  superphos- 
phate of  lime,  and  insoluble  CaS04. 

Ca3(P04)2  +  2  H2S04  =  H4Ca(P04)2  +  2  CaSO4. 

This  completes  the  process  for  fertilizers.  If  P  is  desired,  the  above  is 
filtered ;  charcoal,  a  reducing  agent,  is  added  to  the  filtrate ;  the  substance 
is  evaporated,  then  very  strongly  heated  and  distilled  in  retorts,  the  necks 
of  which  dip  under  water.  It  is  then  purified  from  any  uncombined  C  by 
melting  in  hot  water  and  passing  into  molds  in  cold  water. 

The  work  is  very  dangerous  and  injurious,  on  account  of  the  low  burn- 
ing-point of  P,  and  its  poisonous  properties.  While  its  compounds  are 
necessary  to  human  life,  P  itself  destroys  the  bones,  particularly  the  jaw 
bones,  of  the  workers  in  it. 

Between  1,000  and  2,000  tons  are  made  yearly,  mostly  for  matches,  b*jt 
almost  all  at  two  factories,  one  in  England,  and  one  in  France. 


124  PHOSPHORUS. 

202.  Properties.  —  P  is  a  colorless,  transparent  solid, 
when  pure;   the  impure  article  is  yellowish,  translucent, 
and  waxy.     It  is  insoluble    in  water,  slightly  soluble  in 
alcohol  and  ether,  and  it  readily  dissolves  in  CS2,  oil  of 
turpentine,  etc.     Fumes,  having  a  garlic  odor,  rise  when  it 
is  exposed  to  the  air,  and  in  the  dark  it  is  phosphorescent, 
emitting  a  greenish  light. 

203.  Uses.  —  The   uses   of  this   element  and  its   com- 
pounds are  for  fertilizers,   matches,   vermin  poisons,  and 
chemical  operations. 

204.  Matches. — The  use  of  P  for  matches  depends  on 
its  low  burning-point.      Prepared  wood   is    dipped    into 
melted  S,  and  the  end  is  then  pressed  against  a  stone  slab 
having  on  it  a  paste  of  P,  KC1O3,  and  glue.     KNO3  is  often 
used  instead  of  KC1O3.      In  either  case  the  object  is  to 
furnish   O  to  burn  P.      Matches  containing  KC1O3  snap 
on   being  scratched,  while  those  having  KNO3  burn  qui- 
etly.      The    friction   from  scratching  a  match  generates 
heat  enough  to  ignite  the  P,  that  enough  to  set  the  S  on 
fire,  and  the  S  enough  to  burn  the  wood.     Give  the  re- 
action  for  each.      Paraffine  is  much   used  instead  of  S. 
Safety  matches  have  no  P,  and  must  be  scratched  on  a 

surface  of  red  P  and  Sb2S3,  or  on  glass. 

\      • 

205.  Ked  Phosphorus. — Two  or  three  allotropic  forms  of  P 
are  known,  the  principal  one  being  red.     If  heated  between   230°  and 
260°,  away  from  air,  the  yellow  variety  changes  to  red,  which  can  be  kept 
at  all  temperatures  below  260°.     Above  that  it  changes  back.     Red  P  is 
not  poisonous,  ignites  only  at  a  high  temperature,  and  is  not  phosphores- 
cent, like  the 


PHOSPHORUS. 


125 


2O6.  Spontaneous  Combustion  of  Phosphene,  or  Hy- 
drogen Phosphide,  PH3. 

Experiment  114.— Put  into  a  200CC  flask  is  P  and  50CC  saturated 
solution  NaOH  or  KOH.  Connect  with  the  p.t.  by  a  long  d.t.,  as  in 
Figure  44,  the  end  of  which  must  be  kept  under  water.  Pour  3  or 
4CC  of  ether  into  the  flask,  to  drive  out  the  air.  It  is  necessary  to  exclude 
all  air,  as  a  dangerously  explosive  mixture  is  formed  with  it.  Heat  the 


Fig.  44. 

mixture,  and  as  the  gas  passes  over  and  into  the  air,  it  takes  fire  spon- 
taneously, and  rings  of  smoke  successively  rise.  It  will  do  no  harm  if, 
on  taking  away  the  lamp,  the  water  is  drawn  back  into  the  flask ;  but 
in  that  case  the  flask  should  be  slightly  lifted  to  prevent  breakage  by 
the  sudden  rush  of  water.  On  no  account  let  the  air  be  drawn  over. 
The  experiment  has  no  practical  value,  but  is  an  interesting  illus- 
tration of  the  spontaneous  combustion  of  PH3  and  of  vortex  rings. 
What  are  the  products  of  the  combustion  ?  An  admixture  of  another 
compound  of  P  and  H  causes  the  combustion. 


CHAPTER   XL. 

ARSENIC. 

Examine  metallic  arsenic,  realgar,  orpiment,  arsenopyrite,  arsenic 
trioxide,  copper  arsenite. 

The  compounds  of  arsenic  are  very  poisonous  if  taken  into  the  sys- 
tem, and  must  be  handled  with  care. 

2O7.    Separation. 

Experiment  115.  —  Draw  out  into  two  parts  in  the  Bun- 
sen  flame  a  piece  of  glass  tubing  20cm  long  and  1  or  2cm  in 
diameter.  Into  the  end  of  one  of  the  ignition  tubes  thus 
formed,  when  it  is  cool,  put  one-fourth  of  a  gram  of  arsenic 
trioxide,  As2O3,  using  paper  to  transfer  it.  Now  put  into 
the  tube  a  piece  of  charcoal,  and  press  it  down  to  within  2 
or  3cm  of  the  As.2O3  (Fig.  45).  Next  heat  the  coal  red-hot, 
and  then  at  once  heat  the  As2O3.  Continue  this  process  till 
you  see  a  metallic  sublimate  —  metallic  mirror  —  on  the  tube 
above  the  coal.  Break  the  tube  and  examine  the  sublimate. 
It  is  As.  Heat  vaporizes  the  As2O3.  Explain  the  chemi- 
cal action.  What  is  the  agency  of  C  in  the  experiment? 
Of  As2O37  2As2O3  +  3C  =  ? 

/ 

2O8.    Tests.  —  Experiments    115    and   116    are 

used  as  tests  for  the  presence  of  arsenic. 

Experiment  116.  —  Prepare  a  H  generator,  —  a  flask  with 
a  thistle-tube  and  a  philosopher's  lamp  tube  (Fig.  46),  put  in  some 
granulated  Zn,  water,  and  HC1.  Test  the  purity  of  the  escaping  gas 
(Experiment  23),  and  when  pure,  light  the  jet  of  H.  H  is  now  burning 
in  air.  To  be  sure  that  there  is  no  As  in  the  ingredients  used,  hold 
the  inside  of  a  porcelain  evaporating-dish  directly  against  the  flame 


ARSENIC.  127 

for  a  minute.  If  no  silvery-white  mirror  is  found,  the  chemicals 
are  free  from  As.  Then  pour  through  the  thistle-tube,  while  the 
lamp  is  still  burning,  lcc  solution  of  Ag2O3  in  HC1  or  H2O  —  a  bit  of 
As2O3  not  larger  than  a  grain  of  wheat  in  10CC  HC1. 
See  whether  the  color  of  the  flame  changes ;  then  hold 
the  evaporating-dish  once  more  in  the  flame,  and  no- 
tice a  metallic  deposit  of  As.  Set  away  the  appara- 
tus under  the  hood  and  leave  the  light  burning. 

This  experiment  must  not  be  performed  unless  all 
the  cautions  are  observed,  since  the  gas  in  the  flask 
(AsH3)  is  the  most  poisonous  known,  and  a  single 
bubble  of  it  inhaled  is  said  to  have  killed  the  dis- 
coverer. By  confining  the  gas  inside  the  flask  there  i 
is  no  danger. 

Instead  of  using  As2O3  solution,  a  little  Paris  green,          F.      4 
wall  paper  suspected   of    containing    arsenic,   green 
silk,  or  green  paper  labels,  etc.,  may  be  soaked  in  HC1,  and  tested. 

209.  Explanation.  —  The  chemical  changes  are  as  fol- 
lows :  The  compounds  of  As,  in  this  case  As2O3,  in  presence 
of  nascent  H,  are  immediately  converted  into  the  deadly 
hydrogen  arsenide  (arsine,  arseniuretted  hydrogen),  AsH3. 
As2O3+12H  =  2AsH3  +  3H2O.      The  AsH3   mixed  with 
excess  of  H  tends  to  escape  and  is  burned  to  As2O3  and 
H2O,  and  thus  is  rendered  comparatively  harmless  as  it 
passes  into  the  air.     This  is  why  the  flame  must  be  burn- 
ing when  the  arsenic  compound  is  introduced.     2  AsH3-f- 
6O-As2O3+3H2O. 

In  the  combustion  of  AsH3,  H  burns  at  a  lower  point 
than  As.  The  introduction  of  a  cold  body  like  porcelain 
cools  the  flame  below  the  kindling-point  of  As,  and  this  is 
deposited,  while  H  burns,  in  exactly  the  same  way  as  lamp- 
black was  collected  in  Experiment  26. 

210.  Expert  Analysis.  —  A  modification  of  this  experi- 
ment is  employed  by  experts  to  test  for  AsgOg  poisoning. 


128  ARSENIC. 

The  organs  —  stomach  or  liver  —  are  cut  into  small  pieces 
dissolved  by  nascent  Cl,  or  HC1O,  made  from  KC1O3  and 
HC1,  and  the  solution  is  introduced  into  a  H  generator,  as 
above.  As2O8  preserves  the  tissues  it  comes  in  contact  with, 
for  a  long  time,  and  the  test  can  be  made  years  after  death. 
All  the  chemicals  must  be  pure,  since  As  is  found  in  small 
quantities  in  most  ores,  and  the  Zn,  HC1,  and  H2SO4  of 
commerce  are  very  likely  to  contain  it.  The  above  is 
called  Marsh's  test,  and  is  so  delicate  that  a  mere  trace  of 
arsenic  can  be  detected. 

211.  Properties    and    Occurrence.  —  As  is  a  grayish 
white  solid,  of  metallic  luster,  while  a  few  of  its  charac- 
ters are  non-metallic.     It  is  very  widely  distributed,  being 
sometimes  found  native,  and  sometimes  combined,  as  AsS, 
realgar,  As2S3,  orpiment,  and  FeAsS,  arsenopjaite.      Its 
chief   source   is   the   last,   the    fine    powder  of   which    is 
strongly  heated,  when  As  separates  and  sublimes.     It  has 
the  odor  of  garlic,  as  may  be  observed  by  heating  a  little 
on  charcoal  with  the  blow-pipe. 

212.  Atomic    Volume.  —  As   is   peculiar   in   that  its 
atomic  volume,  so  far  as  the  volume  can  be  determined, 
is  only  half  that  of   the  H   atom.      Its  vapor  density  is 
150,  which  gives  300  for  the  molecular  weight,  while  its 
least  combining  or  atomic  weight  is  75.     300,  the  molec- 
ular weight,  -5-75,  the  atomic  weight,  =  4,  the  number  of 
atoms  in  the  molecule.     All  gaseous  molecules  being  of 
the  same  size,  represented   by  two   squares,  the   atomic 
volume  of  As  must  be  one-fourth  of  this  size,  represented 
by  half  of  one  square,  Q.     Of  what  other  element  is  this 
true  ?     See  page  1£ 


ARSENIC.  129 

% 

213.  Uses  of  As2O3.  —  Arsenic  is  used  in  shot-manu- 
facture, for  hardening  the  metal.  Its  most  important 
compound  is  As2O3,  arsenic  trioxide,  called  also  arsenious 
anhydride,  arsenious  acid,  white  arsenic,  etc.  So  poison- 
ous is  this  that  enough  could  be  piled  on  a  one-cent 
piece  to  kill  a  dozen  persons.  Taken  in  too  large  quan- 
tities it  acts  as  an  emetic.  The  antidote  is  ferric  hydrate 
Fe2(OH)6  and  a  mustard  emetic,  followed  by  oil  or  milk. 

The  vapor  density  of  this  compound  shows  that  its 
symbol  should  be  As4O6,  but  the  improper  one,  As2O3,  is 
likely  to  remain  in  use.  Another  oxide,  As2O5,  arsenic 
pentoxide,  exists,  but  is  less  important.  Show  how  the 
respective  acid  formulae  are  obtained  from  these  anhy- 
drides. See  page  50. 

As2O3  is  used  in  making  Paris  green  (page  165)  ;  in 
many  green  coloring  materials,  in  which  it  exists  as  cop- 
per arsenite ;  in  coloring  wall  papers,  and  in  fly  and  rat 
poisons.  It  is  employed  for  preserving  skins,  etc.  Fash- 
ionable women  sometimes  eat  it  for  the  purpose  of  beauti- 
fying the  complexion,  to  which  it  imparts  a  ghastly  white, 
unhealthy  hue.  Mountaineers  in  some  parts  of  Europe 
eat  it  for  the  greater  power  of  endurance  which  it  is 
supposed  to  give  them.  By  beginning  with  small  doses 
these  arsenic-eaters  finally  consume  a  considerable  quan- 
tity of  the  poison  with  apparent  impunity;  but  as  soon 
as  the  habit  is  stopped,  all  the  pangs  of  arsenic-poisoning 
set  in.  Wall  paper  containing  arsenic  is  said  to  be  in- 
jurious to  some  people,  while  apparently  harmless  to  others. 


CHAPTER   XLIn 

SILICON,  SILICA,   AND   SILICATES. 

214.  Comparison  of  Si  and  C.  —  The  element  Si  resem- 
bles carbon  in  valence  and  in  allotropic  forms.  It  occurs 
in  three  forms  like  C,  —  a  diamond  form,  a  graphite,  and 
an  amorphous.  C  forms  the  basis  of  the  vegetable  and 
animal  world;  Si,  of  the  mineral.  Most  soils  and  rocks, 
except  limestone,  are  mainly  compounds  of  O,  Si,  and 
metals.  While  O  is  estimated  to  make  up  nearly  one- 
half  of  the  known  crust  of  the  earth,  Si  constitutes  fully 
a  third.  The  two  are  usually  combined,  as  silica,  SiO2, 
or  silicates,  SiO2  combined  with  metallic  oxides.  This 
affinity  for  O  is  so  strong  that  Si  is  not  found  uncombined, 
and  is  separated  with  great  difficulty  and  only  at  the  high- 
est temperatures.  No  special  use  has  yet  been  found  for 
it,  except  as  an  alloy  with  Al.  Its  compounds  are  very 
important. 

215  Silica.  —  Examine  some  specimens  of  quartz,  rock 
crystal,  white  and  colored  sands,  agate,  jasper,  flint,  etc. ; 
test  their  hardness  with  a  knife  blade,  and  see  whether 
they  will  scratch  glass.  Notice  that  quartz  crystals  are 
hexagonal  or  six-sided  prisms,  terminated  by  hexagonal 
pyramids.  The  coloring  matters  are  impurities,  often 
Fe  and  Mn,  if  red  or  brown.  When  pure,  quartz  is  trans- 
parent as  glass,  infusible  except  in  the  oxy-hydrogen  blow- 


SILICON,    SILICA,    AND    SILICATES.  131 

pipe,  and   harder   than   glass.      Rock  crystal   is   massive 
SiO2.     Sand  is  generally  either  silica  or  silicates. 

The  common  variety  of  SiO2  is  not  soluble  in  water  or  in  acids,  except  HF. 
An  amorphous  variety  is  to  some  extent  soluble  in  water.  Most  geysers 
deposit  the  latter  in  successive  layers  about  their  mouths.  Agate,  chalced- 
ony, and  opal  have  probably  an  origin  similar  to  this.  A  solution  of  this 
variety  of  Si02  forms  a  jelly-like  mass  —  colloid  —  which  will  not  diffuse 
through  a  membrane  of  parchment  —  dialyzer  —  when  suspended  in  water. 
Crystalloids  will  diffuse  through  such  a  membrane,  if  they  are  in  solution. 
This  principle  forms  the  basis  of  dialysis. 

All  substances  are  supposed  to  be  either  crystalloids,  i.e.  susceptible  of 
crystallization,  or  colloids  —  jelly-like  masses.  HC1  is  the  most  diffusible 
in  liquids  of  all  known  substances;  caramel  is  one  of  the  least  so.  To 
separate  the  two,  they  would  be  put  into  a  dialyzer  suspended  in  water, 
when  HC1  will  diffuse  through  into  the  water,  and  caramel  will  remain. 
As2O3,  in  cases  of  suspected  poisoning,  was  formerly  separated  from  the 
stomach  in  this  way,  as  it  is  a  crystalloid,  whereas  most  of  the  other  con- 
tents of  the  stomach  are  colloidal. 

216.  Silicates.  —  Si  is  a  tetrad  (page  12).    Si02  +  2  H2O  =  ?     SiO2 
-f  H2O  —  7      In  either  case  the  product  is  called   silicic  acid.     Replace 
all  the  H  with  Na,  and  name  the  product.     Replace  it  with  K  ;   Mg;   Fe; 
Pb ;  Ca.   Na4SiO4  and  Na2Si03  are  typical  silicates  of  Na,  but  others  exist. 

217.  Formation  of  SiO2  from  Sodium  Silicate. 

Experiment  117.  —  To  5CC  Na4SiO4  in  an  evaporating-dish  add  5CC 
HC1.  Describe  the  effect.  Pour  away  any  extra  HC1.  Heat  the  resi- 
due gently,  above  a  flame,  till  it  becomes  white,  then  cool  it  and  add 
water.  In  a  few  minutes  taste  a  drop  of  the  water,  then  pour  it  off,  leav- 
ing the  residue.  Crush  a  little  in  the  fingers,  and  compare  it  with 
white  sand,  SiO2.  Apply  to  the  experiment  these  equations  :  — 

Na4SiO4  +  4  HC1  =  4  NaCl  +  H4SiO4.  H4SiO4  -  2  H2O  =  SiO2.  Why 
was  H4Si()4  heated  ?  Why  was  water  finally  added  ? 

Water  glass,  sodium  or  potassium  silicate,  used  somewhat  for  making 
artificial  stone,  is  made  by  fusing  Si02  with  Na2CO3  or  K2C03,  and  dis- 
solving in  water.  Silicic  acid  forms  the  basis  of  a  very  important  series 
of  compounds,  —  the  silicates.  The  above  two  are  the  only  soluble  ones, 
and  may  be  called  liquid  glass.  See  page  172. 


CHAPTER   XLIL 

GLASS  AND  POTTERY. 

Examine  white  sand,  calcium  carbonate,  sodium  carbonate,  smalt ; 
bottle,  window,  Bohemian  and  flint  glass. 

218.  Glass  is  an  Artificial  Silicate.  —  SiO2  alone  is  al- 
most infusible,  as  is  also  CaO ;  but  mixed  and  heated  the 
two  readily  fuse,  forming  calcium  silicate.    CaO  +  SiO2  =  ? 
Notice  that  SiO2  is  the  basis  of  an  acid,  while  CaO  is  essen- 
tially a  base,  and  the  union  of  the  two  forms  a  salt.    There 
are  four  principal  kinds  of  glass:  (1)  Bohemian,  a  silicate 
of  K  and  Ca,  not  easily  fused,  and  hence  used  for  chemical 
apparatus  where  high  temperatures  are  required;  (2)  win- 
dow or  plate  glass,  a  silicate  of  Na  and  Ca;   (3)  bottle 
glass,  a  silicate  of  Na,  Ca,  Al,  Fe,  etc.,  a  variety  which  is 
impure,  and  is  tinged  green  by  salts  of  Fe ;  (4)  flint  glass, 
a  silicate  of  K  and  Pb,  used  for  lenses  in  optical  instru- 
ments, cut  glass  ware,  and,  with  B   added,  for  paste,  or 
imitation  diamonds,  etc.     Pb  gives  to  glass  high  refract- 
ing power,  which  is  a  valuable  property  of  diamonds,  as 
well  as  of  lenses. 

219.  Manufacture.  —  Pure  white  sand,  SiO2,  is  mixed 
with    CaCO3   and   Na2CO3,    some    old   glass — cullet  —  is 
added,  and  the  mixture   is   fused   in  fire-clay    crucibles. 
For  flint  glass,  Pb3O4,  red  lead,  is  employed.     If  color  is 
desired,  mineral  coloring  matter  is  also  added,  but  not 
always  at  this  stage.     CoO,  or  smalt,  gives  blue;  uranium 


GLASS   AND    POTTERY.  133 

oxide,  green  ;  a  mixture  of  Au  and  Sn  of  uncertain  com- 
position, called  the  "purple  of  Cassius,"  gives  purple. 
MnO2  is  used  to  correct  the  green  tint  caused  by  FeO, 
which  it  is  supposed  to  oxidize.  Opacity,  or  enamel, 
as  in  lamp-shades,  is  produced  by  adding  As2O3,  Sb2O3, 
SnO2,  cryolite,  etc.  The  glass- worker  dips  his  blow- 
pipe —  a  hollow  iron  rod  five  or  six  feet  long  —  into  the 
fused  mass  of  glass,  removes  a  small  portion,  rolls  it 
on  a  smooth  surface,  swings  it  round  in  the  air,  blow- 
ing meanwhile  through  the  rod,  and  thus  fashions  it  as 
desired,  into  bottles,  flasks,  etc.  For  some  wares,  e.fy.  com- 
mon goblets,  the  glass  is  run  into  molds  and  stamped ;  for 
others  it  is  blown  and  welded.  All  glass  must  be  annealed, 
i.e.  cooled  slowly,  for  several  days.  The  molecules  thus 
arrange  themselves  naturally.  If  not  annealed,  it  breaks 
very  easily.  It  may  be  greatly  toughened  by  dipping,  when 
nearly  red-hot,  into  hot  oil.  Cut  glass  is  prepared  at  great 
expense  by  subsequent  grinding.  Glass  may  be  rendered 
semi-opaque  by  etching  either  with  HF,  or  with  a  blast 
of  sand. 

220.  Importance. — Few   manufactured   articles    have 
more  importance  than  glass.     Without  it  the  sciences  of 
chemistry,  physics,  astronomy,  microscopic  anatomy,  zool- 
ogy, and  botany,  not  to  mention  its  domestic  uses,  would 
be  almost  impossible. 

221.  Porcelain    and    Pottery.  —  Genuine    porcelain 
and  china-ware  are  made  of   a  fine  clay,   kaolin,  which 
results    from    the    disintegration    of    feldspathic    rocks. 
Bricks   are   baked   clay.      The    FeO   in  common   clay  is 
oxidized  to  Fe2O3,  on  heating,  a  process  which  gives  their 
red  color.      Some  clay,  having  no   Fe,  is  white;    this  is 


134  GLASS    AND   POTTERY. 

used  for  fire-bricks  and  clay  pipes.  That  containing  Fe  is 
too  fusible  for  fire-clay,  which  must  also  have  much  SiO2. 
The  electric  arc,  however,  will  melt  even  this,  and  the 
most  refractory  vessels  are  of  calcium  oxide  or  of  graphite. 
Pottery  is  clay,  molded,  baked,  and  either  glazed,  like 
crockery,  or  unglazed,  like  flower-pots.  Jugs  and  coarse 
earthenware  are  glazed  by  volatilizing  NaCl  in  an  oven 
which  holds  the  porous  material.  This  coats  the  ware 
with  sodium  silicate.  To  glaze  china,  it  is  dipped  into  a 
powder  of  feldspar  and  SiO2  suspended  in  water  and  vin- 
egar, and  then  fused.  If  the  ware  and  glaze  expand  uni- 
formly with  heat,  the  latter  does  not  crack. 


CHAPTER   XLIII. 

METALS  AND    THEIR   ALLOYS. 

222.    Comparison  of  Metals  and   Non-Metals.  —  The 

majority  of  elements  are  metals,  only  about  a  dozen  being 
non-metallic  in  their  properties.  The  division  line  be- 
tween the  two  classes  is  not  very  well  defined;  e.g.  As 
has  certain  properties  which  ally  it  to  metals ;  it  has  other 
properties  which  are  non-metallic.  H  occupies  a  place 
between  the  two  classes.  The  following  are  the  more 
marked  characteristics  of  each  group  :  — 


METALS. 

1.  Metals  arc  solid  at  ordinary 
temperatures,  and  usually  of   high 
specific  gravity. 

Exceptions :  Hg  is  liquid  above 
—39.5°;  Li  is  the  lightest  solid  known ; 
Na  and  K  will  float  on  water. 

2.  Metals  reflect  light  in  a  way 
peculiar  to  themselves.     They  have 
what  is  called  a  metallic  luster. 


3.  They  are  white  or  gray. 
Exceptions :  Au,  Ca,  Sr  are  yel- 
low ;   Cu  is  red. 

4.  In  general  they  conduct  heat 
and  electricity  well. 


NON-METALS. 

1.  Non-metals  are  either  gaseous 
or   solid  at  ordinary  temperatures, 
and  of  low  specific  gravity. 

Exceptions  :  Br  is  a  liquid ;  I  has 
the  heaviest  known  vapor. 

2.  Non-metallic  solids  have  dif- 
ferent  lusters,  as   glassy,  resinous 
silky,  etc. 

Exceptions :    I,  B,  and  C   have 
metallic  luster. 

3.  Non-metals   have  no  charac- 
teristic color. 

4.  They  are  non-conductors  of 
heat  and  electricity. 

Exceptions :    C  and  some  others 
are  conductors. 


136 


METALS   AND   ALLOYS. 


5.  They  are  deficient  in  mallea- 
bility and  ductility. 

6.  They  often  form  liquid  solu- 
tions, similar  to  alloys  in  metals. 


7.  Non-metals  are  electro-nega- 
tive, and  with  H,  or  with  H  and  O, 
form  acids. 


5.  They  are   usually   malleable 
and  ductile. 

6.  They  form  alloys,  or  "  chemi- 
cal  mixtures,"   with    one    another, 
similar  to  other  solutions. 

Exceptions:  Some,  as  Pb  and 
Zn,  will  not  alloy  with  one  another. 

7.  Metals  are  electro-positive  el- 
ements, and  unite  with  O  and  H  to 
form  bases. 

Exceptions-  Some  of  the  less 
electro-positive  metals,  with  a  Itfrge 
quantity  of  0,  form  acids,  as  Cr, 
As,  etc. 

Numbers  2,  6,  and  7  are  the  most 
characteristic  and  important  prop- 
erties. 


Examine  brass,  bronze,  bell-metal,  pewter,  German  silver,  solder, 
type-metal. 

223.  Alloys.  —  An  alloy  is  not  usually  a  definite  chemi- 
cal compound,  but  rather  a  mixture  of  two  or  more  metals 
which  are  melted  together.  One  metal  may  be  said  to  dis- 
solve in  the  other,  as  sugar  dissolves  in  water.  The  alloy 
has,  however,  different  properties  from  those  of  its  elements. 
For  example,  plumber's  solder  melts  at  a  lower  temperature 
than  either  Pb  or  Sn,  of  which  it  is  composed.  Some  metals 
can  alloy  in  any  proportions.  Solder  may  have  two  parts  of 
Sn  to  one  of  Pb,  two  of  Pb  to  one  of  Sn,  or  equal  parts  of 
each,  or  the  two  elements  may  alloy  in  other  proportions. 
Not  all  metals  can  be  thus  fused  together  indefinitely; 
e.g.,  Zn  and  Pb.  Nickel  and  silver  coins  are  alloyed  with 
Cu,  gold  coins  with  Cu  and  Ag. 


Gun-metal,  bell-metal,  and  speculum-metal  are  each  alloys  of  Cu  and 
Sn.    Speculum-metal,  used  for  reflectors  in  telescopes,  has  relatively  more 


METALS   AND  ALLOYS.  137 

Sn  than  either  of  the  others ;  gun-metal  has  the  least.  An  alloy  of  Sb 
and  Pb  is  employed  for  type-metal  as  it  expands  at  the  instant  of  solidifi- 
cation. Pewter  is  composed  of  Sn  and  Pb ;  brass,  of  Cu  and  Zn ;  Ger- 
man silver,  of  brass  and  Ni ;  bronze,  of  Cu,  Sn,  and  Zn ;  aluminium  bronze, 
of  Cu  and  Al. 

224.  Low    Fusibility   is    a   feature    of    many   alloys. 
Wood's  metal,  composed  of  Pb  eight  parts,  Bi  fifteen,  Sn 
four,  Cd  three,  melts  at  just  above  60°,  or  far  below  the 
boiling-point  of  water.     By  varying  the  proportions,  differ- 
ent fusing-points  are  obtained.     This  principle  is  applied  in 
automatic  fire  alarms,  and  in  safety  plugs  for  boilers  and 
fire  extinguishers.      Water  pipes  extend  along  the  ceiling 
of  a  building  and  are  fitted  with  plugs  of  some  fusible 
alloy,  at  short  distances  apart.     When,  in  case  of  fire,  the 
heat  becomes  sufficiently  intense,  these  plugs  melt  and  the 
water  flows  out. 

225.  Amalgams. — An  amalgam  is  an  alloy  of  Hg  and 
another   metal.      Mirrors   are   "silvered"   with  an   amal- 
gam of  Sn.     Tin-foil  is  spread  on  a  smooth  surface  and  cov- 
ered with  Hg,  and  the  glass  is  pressed  thereon. 

Various  amalgams  are  employed  for  filling  teeth,  a  com- 
mon one  being  composed  of  Hg,  Ag,  and  Sn.  Au  or  Ag, 
with  Hg,  forms  an  amalgam  used  for  plating.  Articles  of 
gold  and  silver  should  never  be  brought  in  contact  with 
Hg.  If  a  thin  amalgam  cover  the  surface  of  a  gold  ring  or 
coin,  Hg  can  be  removed  with  HNO3,  as  Au  is  not  attacked 
by  it.  Would  this  acid  do  in  case  of  silver  amalgam? 
Heat  will  also  quickly  cause  Hg  to  evaporate  from  Au. 


CHAPTER   XLIV. 

SODIUM  AND   ITS   COMPOUNDS. 
Examine  NaCl,  Na2SO4,  Na2CO3,  Na,  NaOH,  HNaCO3,  NaNO3. 

226.  Order  of  Derivation.  —  Though  K  is  more  metal- 
lic, or  electro-positive,  than  Na,  the  compounds  of  Na  are 
more  important,  and  will  be  considered  first.  The  only 
two  compo-unds  of  Na  which  occur  extensively  in  nature 
are  NaCl  and  NaNO3.  Almost  all  others  are  obtained 
from  NaCl,  as  shown  by  this  table,  which  should  be  mem- 
orized and  frequently  recalled. 

(  Na 
• 


NaCl         Na2S04      Na2CO3  •    NaOH 
NaN03  <  HNaC°3 

From  what  is  Na2SO4  prepared,  as  shown  by  the  table  ? 

Na2CO3?    Na? 

227.  Occurrence  and  Preparation  of  NaCl.  —  NaCl 
occurs  in  sea  water,  of  which  it  constitutes  about  three 
per  cent,  in  salt  lakes,  whose  waters  sometimes  hold  thirty 
per  cent,  or  are  nearly  saturated,  and,  as  rock  salt,  in  large 
masses  underground.  Poland  has  a  salt  area  of  10,000 
square  miles,  in  some  parts  of  which  the  pure  transparent 
rock  salt  is  a  quarter  of  a  mile  thick.  In  Spain  there  is  a 
mountain  of  salt  five  hundred  feet  high  and  three  miles  in 
circumference.  France  obtains  much  salt  from  sea  water. 
At  high  tide  it  flows  into  shallow  basins,  from  which  the 
sun  evaporates  the  water,  leaving  NaCl  to  crystallize.  In 
Norway  it  is  separated  by  freezing  water,  and  in  Poland  it 


SODIUM   AND   ITS    COMPOUNDS.  139 

is  mined  like  coal.  In  New  York  and  Michigan  it  is  ob- 
tained by  evaporating  the  brine  of  salt  wells,  either  by  air 
and  the  sun's  heat,  or  by  fire.  Slow  evaporation  gives 
large  crystals  ;  rapid,  small  ones. 

228.  Uses.  —  The  main  uses  are  for  domestic  purposes 
and  for  making  the  Na  and  Cl  compounds.     In  the  United 
States    the    consumption    amounts   to    more    than   forty 
pounds  per  year  for  every  person. 

229.  Sodium  Sulphate.  —  What   acid  and  what   base 
are  represented  by  Na2SO4?    Which  is  the  stronger  acid, 
HC1   or   H2SO4?     Would   the    latter   be   apt   to   act   on 
NaCl?     Why? 

230.  Manufacture.  —  This  comprises  two  stages  shown 
by  the  following  reactions,  in  which  the  first  needs  moder- 
ate heat  only ;   the  last,  much  greater. 

(1)  2  NaCl  +  H2S04  -  HNaSO4  +  NaCl  +  HC1. 

(2)  NaCl  +  HNaS04  -  Na2SO4  ~f  HC1. 

The  operation  is  carried  on  in  large  furnaces.  The  gas- 
eous HC1  is  passed  into  towers  containing  falling  water  in 
a  fine  spray,  for  which  it  has  great  affinity.  The  solution  is 
drawn  off  at  the  base  of  the  tower.  Thus  all  commercial 
HC1  is  made  as  a  by-product  in  manufacturing  Na2SO4. 

When  crystalline,  sodium  sulphate  has  ten  molecules 
of  water  of  crystallization  (Na2SO4,  10  H2O) ;  it  is  then 
known  as  Glauber's  salt.  This  salt  readily  effloresces ;  i.e. 
loses  its  water  of  crystallization,  and  is  reduced  to  a 
powder.  Compute  the  percentage  of  water. 

231.  Uses.  —  The  leading  use  of  Na2SO4  is  to  make 
Na2CO3;  it  is  also  used  to  some  extent  in  medicine,  and  in 
glass  manufacture. 


140  SODIUM   AND    ITS   COMPOUNDS. 

232.  Sodium  Carbonate.  —  Note  the  base  and  the  acid 
which  this  salt  represents.     Test  a  solution  of  the  salt  with 
red  and  blue  litmus,  and  notice  the  alkaline  reaction.     Do 
you  see  any  reason  for  this  reaction  in  the  strong  base  and 
the  weak  acid  represented  by  the  salt  ? 

233.  Manufacture.  —  Na2CO3  is  not  made  by  the  union 
of  an  acid  and  a  base,  nor  is  H2CO3  strong  enough  to  act 
on  many  salts.     The  process  must  be  indirect.     This  con- 
sists in  reducing  Na2SO4  to  Na2S,  by  taking  away  the  O 
with  C,  charcoal,  and  then  changing  Na2S  to  Na2CO3  by 
CaCO3,   limestone.      The    three    substances,    Na2SO4,    C, 
CaCO3,  are  mixed  together  and   strongly  heated.      The 
reactions  should  be  carefully  studied,  as  the  process  is  one 
of  much  importance. 

(1)  Na2SO4+  4  C  =  Na2S  -f  4  CO. 

(2)  Na2S  +  CaCO3  =  CaS  +  Na2CO3. 

Observe  that  C  is  the  reducing  agent.  The  gas  CO 
escapes.  The  solid  products  Na2CO3  and  CaS  form  black 
ash,  the  former  being  very  soluble,  the  latter  only  sparingly 
soluble  in  water.  Na2CO3  is  dissolved  out  by  water,  and 
the  water  is  evaporated.  This  gives  commercial  soda. 
CaS,  the  waste  compound  in  the  process,  contains  the  S 
originally  in  the  H2SO4  used.  This  can  be  partially  sepa- 
rated and  again  made  into  acid.  Describe  the  manufac- 
ture of  Na2CO3  in  full,  starting  with  NaCl.  This  is  called 
the  Le  Blanc  process,  but  is  not  the  only  one  now  em- 
ployed to  produce  this  important  article. 

234.  Occurrence.  —  Sodium  carbonate  is  found  native 
in  small  quantities.     It  forms  the  chief  surface  deposit  of 
the  "alkali  belt"  in  western  United  States,  where  it  often 
forms  incrustations  from  an  inch  to  a  foot  in  thickness. 


SODIUM    AND    ITS   COMPOUNDS.  141 

It  was  formerly  obtained  from  sea-weeds,  by  leaching  their 
ashes,  as,  by  a  like  process,  K2CO3  was  obtained  from  land 
plants. 

235.  Uses.  —  Na2CO3  forms  the  basis  of  many  alkalies, 
as  H2SO4  does  of  acids.    Of  all  chemical  compounds  it  is  one 
of  the  most  important,  and  its  manufacture  constitutes  one 
of  the  greatest  chemical  industries.     Its  economical  manu- 
facture largely  depends  on  the  demand  for  HC1,  which  is 
always  formed  as  a  by-product.     As  but  little  HC1  is  used 
in  this  country,  Na2CO3  is  mostly  manufactured  in  Europe. 
The  chief  uses  are  for  glass  (page  132)  and  alkalies. 

236.  Sodium.  —  Na  must  always  be  kept  under  naphtha,  or 
some  other  liquid  compound  containing  no  O,  since  it  oxidizes  at  once 
on  exposure  to  the  air.     For  this  reason  it  never  occurs  in  a  free  state. 

237.  Preparation.  —  By  depriving  Na2CO3  of  C  and  O, 
metallic  sodium  is  formed.     As  usual,  heated  charcoal  is 
the  reducing  agent.     The  end  of  the  retort,  which  holds 
the  mixture,  dips  under  naphtha. 

Na.,CO3  +  2  C  =  2  Na  +  3  CO.  The  process  is  a  difficult 
one,  and  Na  brings  five  dollars  per  pound,  though  in  its 
compounds  it  is  a  third  as  common  as  Fe.  K  is  as  abun- 
dant as  Na,  but  more  difficult  of  separation,  and  is  worth 
three  dollars  per  ounce.  Notice  the  position  of  K  and 
Na  at  the  positive  end  of  the  elements,  page  43. 

238.  Uses.  —  Na  is  used  to  reduce  Al,  Ca,  Mg,  Si,  which 
are  the  most  difficult  elements  to  separate  from  their  com- 
pounds.    It  acts  in  these  cases  as  a  reducing  agent. 

239.  Sodium  Hydrate. 

Review  Experiment  62,  page  69. 


142  SODIUM  AND   ITS   COMPOUNDS. 

Experiment  118.  —  Put  into  a  t.t  lO*  H2O  and  2  or  3*  NaOH. 

Note  its  easy  solubility.     Test  with  litmus.     Will  it  neutralize  any 
acids?    See  page  53. 

240.  Preparation.  —  Sodium  hydrate,  caustic  soda,  or 
soda  by  lime,  is  made  by  treating  a  solution  of  Na2CO3with 
milk  of  lime  (page  69).     CaCO3  is  precipitated   and  al- 
lowed to  settle,  the  solution  is  poured  off,  and  NaOH  is 
obtained  by  evaporating  the  water  and  running  the  residue 
into  molds. 

241.  Use.  —  NaOH  is  a  powerful  caustic,  but  its  chief 
use  is  in  making  hard  soap.    See  page  187. 

242.  Hydrogen  Sodium  Carbonate.  —  Hydrogen    so- 
dium carbonate,  bicarbonate  of  sodium,  acid  sodium  car- 
bonate, cooking-soda,  etc.,  HNaCO3,  is  prepared  by  passing 
CO2  into  a  solution  of  Na2CO3.     Na2CO3  +  H2O  +  CO2  = 
2  HNaCO3.      Test  a  solution  of  it  with  litmus.     Account 
for  the  result.     Its  use  in  bread-making  depends  on  the 
ease  with  which  CO2  is  liberated.     Even  a  weak  acid,  as 
the  lactic  acid  of  sour  milk,  sets  this  free,  and  thus  causes 
the  dough  to  rise. 

243.  Sodium  Nitrate.  —  Sodium  nitrate  occurs  in  Chili 
and  Peru.     It  is  the  main  source  of  HNO3. 

Review  Experiments  46  and  52.  From  NaNO3  is  also 
made  KNO3  (NaNO3  +  KC1  -  NaCl  +  KNO3),  one  of  the 
ingredients  of  gunpowder.  By  reason  of  its  deliquescence 
NaNO3  is  not  suitable  for  making  gunpowder,  though  it  is 
sometimes  used  for  blasting-powder.  The  action  of  the 
latter  is  slower  than  that  made  from  KNO3.  NaNO3  is 
cheaper  and  more  abundant  than  KNO3;  this  is  true  of 
most  Na  compounds  in  comparison  with  those  of  K. 


CHAPTER   XLV. 

POTASSIUM    AND    AMMONIUM. 
POTASSIUM    AND    ITS   COMPOUNDS. 

Examine  K,  KC1,  K2SO4,  K2CO3,  KOH,  HKCO3,  KC1O3,  KCN. 

244.  Occurrence  and  Preparation.  —  Potassium  oc- 
curs only  in  combination,  chiefly  as  silicates,  in  such 
minerals  as  feldspar  and  mica.  By  their  disintegration  it 
forms  a  part  of  soils  from  which  such  portions  as  are  solu- 
ble are  taken  up  by  plants.  The  ashes  of  land-plants  .are 
leached  in  pots  to  dissolve  K2CO3 ;  hence  it  is  called  pot- 
ash. Sea-plants  likewise  give  rise  to  Na2CO3.  Wood  ashes 
originally  formed  the  main  source  of  K2CO3.  From  plants 
this  substance  is  taken  into  the  animal  system,  and  makes 
a  portion  of  its  tissue.  Sheep  excrete  it  in  sweat,  which  is 
then  absorbed  by  their  wool.  Large  quantities  are  now 
obtained  by  washing  wool  and  evaporating  the  water. 

K2CO3  and  other  compounds  of  K  are  mainly, derived 
from  KC1,  beds  of  which  exist  in  Germany. 

In  the  following  list  each  K  compound  is  prepared  like  the  same  Na 
compound,  and  the  uses  of  each  of  the  former  are  similar  to  those  of  the 
latter.  K  compounds  are  made  in  much  smaller  quantities  than  those  of 
^fa,  as  KC1  is  far  less  common  than  NaCl. 

(  K 

KC1      {  K2S04  j  K2C03  -j  KOH 
KNO.  <  HKC03 

Examine  specimens  of  each,  side  by  side  with  like  Na  compounds. 
Describe  in  full  their  preparation,  giving  the  reactions.  Also,  perform  the 


144  POTASSIUM  AND   AMMONIUM. 

experiments  given  under  Na,  substituting  K  therefor.     From  KOH  are 
made  KC1O3  and  KCN. 

KOH{KCK>3          -      , 

245.  Potassium  Chlorate.  —  KC1O3  is  made  by  passing  Cl 
into  a  hot  concentrated  solution  of  KOH. 

6  KOH  +  6  Cl  =  KC103  +  5  KC1  +  3  H2O. 
Its  uses  are  in  making  O,  and  as  an  oxidizing  agent. 

246.  Potassium  Cyanide,  KCN,  is  a  salt  from  HCN  —  hydrocy- 
anic or  prussic  acid.     Each  is  about  equally  poisonous,  and  more  so  than 
any  other  known  substance.     A  drop  of  pure  HCN  on  the  tongue  will 
produce   death   quickly  by  absorption   into  the  system.      In  examining 
these  compounds  take  care  not  to  handle  them  or  to  inhale  the  fumes. 
KCN  is  used  as  a  solvent  for  metals  in  electro-plating,  and  is  the  source 
of   many  cyanides,   i.e.  compounds  of   CN  and  a  metal.      KCN  is  em- 
ployed to  kill  insects  for  cabinet  specimens.      In  a  wide-mouthed  bottle 
is  placed  a  little  KCN,  which  is  covered  with  cotton,  and  over  this  a  per- 
forated  paper.      The  bottle  is  inverted  over  the  insect,  and  the  fumes 
destroy  life  without  injuring  the  delicate  parts.     HCN  is  made  from  KCN 
and  H2S04. 

247.  Gunpowder.  —  Gunpowder  is  a  mixture  of  KNO3, 
C,  and  S.     Heat  or  concussion  causes  a  chemical  change, 
and  transforms  the  solids  into  gases.     These  gases  at  the 
moment  of  explosion  occupy  1500  or  more  times  the  vol- 
ume of  the  solids.     Hence  the  great  rending  power  of  pow- 
der.    If  not  confined,  powder  burns  quietly  but  quickly. 
The  appended  reaction  is  a  part  of  what  takes  place,  but 
it  by  no  means  represents  all  the  chemical  changes. 


From  this  equation  compute  the  percentage,  by  weight,  of 
each  substance  used  to  make  gunpowder  economically. 

Thoroughly  burned  charcoal,  distilled  sulphur,  and  the 
purest  nitre  are  powdered  and  mixed  in  a  revolving  drum, 


POTASSIUM  AND   AMMONIUM.  145 

made  into  a  paste  with  water,  put  under  great  pressure* 
between  sheets  of  gun  metal,  granulated,  sifted,  to  sepa- 
rate the  coarse  and  fine  grains,  and  glazed  by  revolving  in 
a  barrel  which  sometimes  contains  a  little  powdered  graph- 
ite. 

Experiment  119.  —  Pulverize  and  mix  intimately  4s  KNO3,  $*  S, 
),s  charcoal.  Pile  the  mixture  on  a  brick,  and  apply  a  lighted  match. 
The  adhering  product  can  be  removed  by  soaking  in  water. 

AMMONIUM    COMPOUNDS. 

248.  Read  the  chapter  on  NH3.  Also,  review  the  experiments  on 
bases.  Examine  NH4C1,  NH4NO3,  (NH4)2S04,  (NH4)2CO3. 

Ammonium,  NH4,  is  too  unstable  to  exist  alone,  but  it 
forms  salts  similar  to  those  of  K  and  Na.  NH3  dissolved 
in  water  forms  NH4OH. 

The  food  of  plants,  as  well  as  that  of  animals,  must  con- 
tain N.  It  has  not  yet  been  shown  that  they  can  make 
use  of  that  contained  in  the  air,  but  they  do  absorb  its 
compounds  from  the  soil.  All  fertilizers  and  manures  con- 
tain a  soluble  compound  of  NH4.  All  NH4  compounds 
are  now  obtained  either  from  coal,  in  making  illuminating- 
gas,  or  from  bones,  by  distillation. 

Suppose  the  product  obtained  from  the  gas-house  to  be  NH4OH,  how 
would  NH4C1  be  made  ?  .  (NH4)2S04  ?  NH4NO3  1  Write  the  reactions. 
(NH4)2CO3  is  made  by  heating  NH4C1  with  CaC03.  Give  the  reaction. 


CHAPTER   XLVI. 

CALCIUM  COMPOUNDS. 

Examine  CaCO3  —  marble,  limestone,  chalk,  not  crayon,  —  CaSO4 
—  gypsum  or  selenite  —  CaCl2,  CaO. 

249.  Occurrence.  —  The  above  are  the  chief  compounds 
of  Ca.     The  element  itself  is  not  found  uncombined,  is 
very  difficult  to  reduce  (page  141),  is  a  yellow  metal,  and 
has  no  use.    Its  most  abundant  compound  is  CaCO3.    Shells 
of  oysters,  clams,  snails,  etc.,  are  mainly  CaCO3,  and  coral 
reefs,  sometimes  extending  thousands  of  miles  in  the  ocean, 
are  the  same.     CaCO3  dissolves  in  water  holding  CO2,  and 
thence    these   marine    animals   obtain   it   and   therefrom 
secrete  their  bony  framework.     All  mountains  were  first 
laid  down  on  the  sea  bottom  layer  by  layer,  and  afterwards 
lifted  up  by  pressure.     Rocks  and  mountains  of  CaCO3 
were  formed  by  marine  animals,  and  all  large  masses  of 
CaCO3  are  thought  to  have  been  at  one  time  the  frame- 
work  of    animals.      Marble   is   crystallized,   transformed 
limestone.     The  process,  called  metamorphism,  took  place 
in  the  depths  of  the  earth,  where  the  heat  is  greater  than 
at  the  surface. 

250.  Lime.  — If   CaCO3  be  roasted   with   C,    CO2   es- 
capes and  CaO  is  left.     CaCO3-CO2  =  ?     This  is  called 
burning  lime,  and  is  a  large  industry  in  limestone  coun- 
tries.    CaO  is  unslaked  lime,  quicklime  or  calcium   ox- 
ide.     It  may  be   slaked   either   by  exposure  to  the  air, 


CALCIUM    COMPOUNDS.  147 

air-slaking,  when  it  gradually  takes  up  H2O  and  CO2 ;  or  by 
mixing  with  H2O,  water-slaking.  CaO  +  H2O  =  Ca(OH)2. 
Great  heat  is  generated  in  the  latter  case,  though  not  so 
much  as  in  the  formation  of  KOH  and  NaOH.  Like  them, 
Ca(OH)2  dissolves  in  water,  forming  lime-water.  Milk  of 
lime,  cream  of  lime,  etc.,  consist  of  particles  of  Ca(OH)2 
suspended  in  H2O. 

251.  Uses  of  Lime. —  CaO  is  infusible  at  the  highest 
temperatures.     If  it  be  introduced  into  the  oxy-hydrogen 
blow-pipe  (page  28),  a  brilliant  light,  second  only  to  the 
electric,  is  produced.      Mortar  is  made  by  mixing  CaO, 
H2O,  and   SiO2.      It   hardens   by  evaporating   the    extra 
H2O,  absorbing  CO2  from  the  air,  and  uniting  with  SiO2  to 
form  calcium  silicate.    It  often  continues  to  absorb  CO2  for 
hundreds  or  thousands  of  years  before  being  saturated,  as 
is  found  in  the  Egyptian  pyramids.     Hence  the  tenacity 
of  old  mortar.     Hydraulic  mortar  contains  silicates  of  Al 
and  Ca,  and  is  not  affected  by  water.     What  are  the  uses 
of  mortar?     Being  the  important  constituent  of  mortar 
and  plaster,  lime  is  the  most  useful  of  the  bases. 

252.  Hard  Water.  —  Review   Experiment   76.      The 
solubility  of  CaCO3  in  water  that  contains  CO2  leads  to 
important  results.      Much  dissolves  in  the  waters  of   all 
limestone    countries;    and    the    water,    though   perfectly 
transparent,  is  hard ;  i.e.  soap  has  little  action  on  it.     See 
page  187.    Such  water  may  be  softened  by  boiling,  a  deposit 
of  CaCO3  being  formed  as  a  crust  on  the  kettle.     Such 
water  is  called  water  of  temporary  hardness.     MgCO3  pro- 
duces a  similar  effect,  and  water  containing  it  is  softened 
in  the  same  way.     Permanently  hard  waters  contain  the 
sulphates  of  Ca  and  Mg,  which  cannot  be  removed  by 
boiling,  but  may  be  by  adding  (NH4)2CO3. 


148  COMPOUNDS   OF   CALCIUM. 

253.  The  Formation  of  Caves  in  limestone  rocks  is 
due  also  to  the  solubility  of  CaCO3.     Water  collects  on 
the  mountains  and  trickles  down  through  crevices,  dissolv- 
ing, if  it  contains  CO2,  some   of  the    CaCO3,  and   thus 
making  a  wider  opening,  and  forcing  its  way  along  fissures 
and  lines  of  least  resistance  into  the  interior  of  the  earth, 
or  out  at  the  base  of  the  mountain.     Its  channel  widens 
as  it  dissolves  the  rock,  and  the  stream  enlarges  until  in 
the  course  of  ages  an  immense  casern  may  be  formed,  with 
labyrinths  extending  for  miles,  from  the  entrance  of  which 
a  river  often  issues.     In  the  long  ages  which  elapsed  dur- 
ing the  slow  formation  of  Mammoth   Cave  its  denizens 
lost  many  of  the  characters  of  their  ancestors,  and  eyeless 
fish  and  also  eyeless  insects  now  abound  there. 

254.  Reverse  Action.  —  Drops  of  water  on  the  roofs  of 
these  caverns  lose -their  CO2  and  deposit  CaCO3.     Thus 
long,  pendant  masses  of  limestone,  called  stalactites,  are 
slowly  formed  on  the  roofs  like  icicles.     From  these,  water 
charged  with  CaCO3  drops  to  the  bottom,  loses  CO2  and 
deposits  CaCO3,  which  forms  an   upward-growing   mass, 
called  stalagmite.      In  time  it  may  meet  the  stalactite  and 
form  a  pillar.     Notice  that  the  same  action  which  formed 
the  cave  is  filling  it  up ;   i.e.  the  solubility  of  CaCO3  in 
water  charged  with  CO2. 

255.  Famous  Marbles.  —  The    marble    from    Carrara, 
Italy,  is  most  esteemed  on  account  of  a  pinkish  tint  given 
by  a  trace  of  oxide  of  iron.     The  best  of  Grecian  marble 
was  from  Paros,  one  of  the  Cyclades.     The  isles  of  the 
Mediterranean  are   of  limestone,  or  of  volcanic,  origin, 
often  of  both. 


149 

256.  Calcium    Sulphate    occurs   in   two    forms,    (1) 
with  water  of  crystallization  —  gypsum,  CaSO4  +  2H2O, 
—  (2)  without  it  —  anhydrite,  CaSO4.     The   former,  on 
being   strongly  heated,   gives    up   its   water,    and  is   re- 
duced to   a  powder  —  plaster  of  Paris.      This,  on  being 
mixed  with  water,  again  takes  up   2  H2O,  and   hardens, 
or  sets,  without  crystallizing.     If  once   more   heated   to 
expel  water,  it  will  not  again  absorb  it.     When  plaster 
of  Paris  sets,  it  expands  slightly,  and  on  this  account  is 
admirable  for  taking  casts. 

257.  Uses.  —  Gypsum  finds  use  as  a  fertilizer  and  as 
an  adulterant  in  coloring-materials,  etc. 

CaSO4  is  employed  in  making  casts,  molds,  statuettes, 
wall-plaster,  crayons,  etc. 

How  can  CaCl2  be  made  "?  What  is  its  use  ?  See  page  27.  What  else  is 
used  for  a  similar  purpose  ? 

Symbolize  and  name  the  acid  represented  by  Ca(C10)2,  and  name  this 
salt  (page  107).  It  is  one  of  the  constituents  of  bleaching-powder, 
the  symbol  of  which,  though  still  under  discussion,  may  be  considered 
Ca(C10)2  +  CaCl2.  This  is  made  by  passing  Cl  over  Ca(OH)2. 
2  Ca(OH)a  +  4  Cl  =  Ca(C10)2  +  CaCl2  +  2  H20. 


CHAPTER   XLVII. 

MAGNESIUM,   ALUMINIUM,  AND  ZINC. 

MAGNESIUM   AND    ITS   COMPOUNDS. 

Examine  magnesite,  dolomite,  talc,  serpentine,  hornblende,  meer= 
schaum,  magnesium  ribbon,  magnesia  alba,  Epsom  salt. 

258.  Occurrence     and    Preparation.  —  Mg    is    very 
widely  distributed,  but  does  not  occur  uncombined.     Its 
salts  are  found  in  rocks  and  soils,  in  sea  water  and  in  the 
water  of  some  springs,  to  which  they  impart  a  brackish 
taste. 

The  most  common  minerals  containing  Mg  are  magne- 
site, MgCO3,  dolomite,  MgCO3+CaCO3,  and  talc,  serpen- 
tine, hornblende,  and  meerschaum.  The  last  four  are 
silicates,  and  often  are  unctious  to  the  touch.  What 
proportion  of  the  earth's  crust  is  composed  of  Mg?  See 
page  173. 

259.  Metallic  Mg1  is  prepared  by  fusing   MgCl2  with 
Na.     Why  is  the  process  expensive  ?    Write  the  reaction. 

Experiment  120.  —  With  forceps  hold  a  short  strip  of  Mg  ribbon 
in  a  flame.  Note  the  brilliancy  of  the  light,  and  give  the  reaction. 
Examine  and  name  the  product. 

Photographs  of  the  interior  of  caverns,  where  sunlight 
does  not  penetrate,  are  taken  by  Mg  light.  Gun-cotton 
sprinkled  with  powdered  Mg  has  recently  been  employed 
for  that  purpose.  Mg  tarnishes  slightly  in  moist  air. 


MAGNESIUM,   ALUMINIUM,    AND    ZINC.  151 

Compounds  of  Mg".  —  MgO,  magnesia,  like  CaO,  is  very  infusible, 
and  is  used  for  crucibles.  Magnesia  alba,  a  variable  mixture  of  MgC03 
and  Mg(OH)2,  is  employed  in  medicine,  as  is  also  Epsom  salt,  MgSO4  + 
7H2O. 

ALUMINIUM   AND   ITS   COMPOUNDS. 

Examine  aluminium,  aluminium  bronze,  corundum,  emery,  feld- 
spar, argillite,  clay.  Note  especially  the  color,  luster,  specific  gravity 
and  flexibility  of  Al. 

What  elements  are  more  common  in  the  earth  than  Al?  What 
metals  ?  See  page  173.  Compare  the  abundance  of  Al  with  that  of 
Fe. 

260.  Compounds  of  Al.  —  Al  occurs  only  in  combina- 
tion with  other  elements.     Feldspar,  mica,  slate,  and  clay 
are  silicates  of  it.     It  occurs  in  all  rocks  except  CaCO3 
and  SiO2,  and  in  nearly  200  minerals.     Though  found  in 
all  soils,  its  compounds  are  not  taken  up  by  plants,  except 
by  a  few  cryptogams.      Corundum,  A12O3,  is  the  richest  of 
its  ores.     Compute  its  per  cent  of  Al.  •  Compounds  of  Al 
are  very  infusible  and  difficult  of  reduction. 

261.  Reduction.  —  Like  most  other  metals  not  easily 
reducible  by  C  or  H,  it  was  originally  obtained  by  electrol- 
ysis, but  more  recently  from  its  chloride,  by  the  reducing 
action  of    strongly   heated    K   or   Na.       A12C16  +  6  Na  = 
6NaCl  +  2Al. 

What  is  the  chief  use  of  Na?  See  page  141.  As  it 
takes  three  pounds  of  Na  to  make  one  pound  of  Al,  the 
cost  of  the  latter  has  been  fifteen  dollars  or  more  per  pound. 
Its  use  has  thus  been  restricted  to  light  apparatus  and 
aluminium  bronze,  an  alloy  of  Cu  90,  Al  10,  which  is  not 
unlike  gold  in  appearance. 

A12O3  has  lately  been  reduced  by  C.  Higher  tempera- 
tures than  have  heretofore  been  known  are  obtained  by 
means  of  the  electric  arc  and  large  dynamo  machines.  A 


152  MAGNESIUM,   ALtTMIKltTM,   AKD    ZINC. 

furnace  made  of  graphite,  because  fire-clay  melts  like  wax 
at  such  a  high  temperature,  is  filled  with  A12O3  —  corun- 
dum,—  C,  and  Cu.  In  the  midst  of  this  are  embedded 
large  carbon  terminals,  connected  with  dynamos.  The 
reduction  takes  several  hours. 

The  following  reaction  takes  place :  A12O3  +  3  C  =  2  Al 
+  3  CO.  Cu  is  also  added,  and  an  alloy  of  Al  and  Cu  is 
thus  formed.  This  alloy  is  not  easily  separable  into  its  ele- 
ments. Explain  the  action  of  the  C.  CO  escapes  through 
perforations  in  the  top  of  the  furnace,  burning  there  to 
CO2.  Only  alloys  of  Al  have  yet  been  obtained  by  this 
process.  This  method  has  not  been  employed  before,  sim- 
ply because  the  highest  temperatures  of  combustion,  2000° 
or  2500°,  would  not  effect  a  reduction.  In  the  same  way 
Si,  B,  K,  Na^  Ca,  Mg,  Cr,  have  recently  been  reduced  from 
their  oxides ;  but  a  process  has  yet  to  be  found  for  sepa- 
rating them  easily  from  their  alloys. 

262.  Properties  and  Uses.  —  Al  is  a  silvery  white 
metal,  lighter  than  glass,  and  only  one-third  the  weight 
of  iron.  It  does  not  readily  rust  or  oxidize,  it  fuses  at 
1000°  (compare  with  Fe),  is  unaffected  by  acids,  except  by 
HC1  and,  slightly,  by  H2SO4j  is  a  good  conductor  of  elec- 
tricity, can  be  cast  and  hammered,  and  alloys  with  most 
metals,  forming  thus  many  valuable  compounds.  Every 
clay-bank  is  a  mine  of  this  metal,  which  has  so  many  of 
the  useful  properties  of  metals  and  has  so  few  defects 
that,  if  it  could  be  obtained  in  sufficient  quantities,  it 
might,  for  many  purposes,  take  the  place  of  iron,  steel, 
tin,  and  other  metals.  From  its  properties  state  any  ad- 
vantages which  it  would  have  over  iron  in  ocean  vessels, 
railroads,  and  bridges.  Why  is  it  better  than  Sn  or  Cu 
for  culinary  utensils  ? 


MAGNESIUM,    ALUMINIUM,   AND  ZINC.  158 

An  alloy  of  Al,  Cu,  and  Si  is  used  for  telephone  wires  in  Europe,  and 
the  Bennett-Mackay  cable  is  of  the  same  material.  Washington  monu- 
ment, the  tallest  shaft  in  the  world,  is  capped  with  a  pyramid  of  Al,  ten 
inches  high. 

For  the  uses  of  alumina,  A1203,  and  its  silicates,  see  page  133. 


ZINC    AND   ITS   COMPOUNDS. 

Examine  zincite,  sphalerite,  Smithsonite,  sheet  zinc,  galvanized 
iron,  granulated  zinc,  zinc  dust. 

263.  Compounds.  —  The  compounds  of  zinc  are  abun- 
dant.   Its  chief  ores  are  zincite,  ZnO,  sphalerite  or  blende, 
ZnS,  Smithsonite,  ZnCO3.     For  their  reduction  these  ores 
are  first  roasted,  i.e.  heated  in  presence  of  air.     With  ZnS 
this  reaction  takes  place  :    ZnS  -f  3  O  =  ZnO  -f  SO2.     The 
oxide  is  reduced  with  C,  and  then  Zn  is  distilled.     State 
the  reaction.     Zinc  is  sublimed  —  in  the  form  of  zinc  dust 
—  like  flowers  of  S.     Granulated  Zn  is  made  by  pouring  a 
stream  of  the  molten  metal  into  water. 

Experiment  121.  —  Burn  a  strip  of  Zn  foil,  and  note  the  color 
of  the  flame  and  of  the  product.  State  the  reaction.  The  red  color 
of  zincite  is  supposed  to  be  imparted  by  Mn  present  in  the  compound. 

264.  Uses.  —  Name  any  use  of  Zn  in  the  chemical  lab- 
oratory.    It  is  employed  for  coating  wire  and  sheet  iron 

—  galvanized  iron.  This  is  done  by  plunging  the  wire 
or  the  sheets  of  iron  into  melted  Zri.  Describe  the  use  of 
Zn  as  an  alloy.  See  page  136. 

ZnO  forms  the  basis  of  a  white  paint  called  zinc  white.  White  vitriol, 
ZnS04  +  7  H20,  is  employed  in  medicine.  Name  two  other  vitriols. 


CHAPTER   XLVIII. 

IRON  AND  ITS    COMPOUNDS. 

Examine  magnetite,  hematite,  limonite,  siderite,  pig-iron,  wrought- 
iron,  steel. 

265.  Ores  and  Irons.  —  As  Fe  occurs  native  only  in 
meteorites  and  in  small  quantities  of  terrestrial  origin,  it  is 
obtained  from  its  ores.     There  are  four  of  these  ores  —  mag- 
netite   (Fe3O4),    hematite    (Fe2O3),    limonite    (2  Fe2O3  + 
3  H2O),  and  siderite  (FeCO3).     Which  is  richest  in  Fe? 
Compute  the  proportion.    FeCO3  occurs  mostly  in  Europe. 
The  reduction  of  these  ores,  as  well  as  of  other  metallic 
oxides,  consists  in  removing  O  by  C  at  a  high  tempera- 
ture.    As  ordinarily  classified  there  are  three  kinds  of 
iron,  —  pig-  or  cast-iron,  steel,  and  wrought-iron. 

Study  this  table,  noting  the  purity,  the  fusing-point,  and 
the  per  cent  of  C  in  each  case. 

Per  Cent 
C. 

2-6 
0.5-2 
Fraction. 

Pure  iron  melts  at  about  1800°.  Pig-iron  is  obtained 
from  the  ore  by  smelting,  and  from  this  are  made  steel 
and  wrought-iron. 

266.  Pig-iron.  —  The  ore  is  reduced  in  a  blast  furnace 
(Fig.  47),  in  some  cases  eighty  or  one  hundred  feet  high, 
and  having  a  capacity  of  about  12,000  cubic  feet.     The 
reducing  agent  is  either  charcoal,  anthracite  coal,  or  coke, 


Pie  . 

Per  Cent  Fe 
(general). 

.     .     .     .        90 

Fusibility. 
1200° 

Steel 

.     .        99 

1400° 

Wrouerht  . 

99.7 

1500° 

IRON   AND   ITS   COMPOUNDS.  155 

bituminous  coal  being  too  impure.  Charcoal  is  the  best 
agent,  and  is  used  in  preparing  Swedish  iron ;  but  it  is 
too  expensive  for  general  use. 


Fig.  47. 

Blast  furnace.  F,  entrance  of  tuyeres,  or  blast-pipes.  E,  F,  hottest  part.  C,  con. 
ductor  for  gases,  which  are  subsequently  used  to  heat  the  air  going  into  the  tuyeres. 
G,  upper  portion,  slag,  lower  portion,  melted  iron. 

Were  ores  absolutely  pure,  only  C  would  be  needed 
to  reduce  them.  Complete:  Fe3O4  +  4C=?  Fe3O4  + 
2C  =  ? 

Much  earthy  material  —  gangue  —  containing  silica  and 
silicates  is  always  found  with  iron  ores.  These  are  infusi- 


156  IRON   AND   ITS   COMPOUNDS. 

ble,  and  something  must  be  added  to  render  them  fusible. 
CaO  forms  with  SiO2  just  the  flux  needed.  See  page  132. 
CaO  +  SiO2=?  Which  of  these  is  the  basic,  and  which 
the  acidic  compound?  CaO  results  from  heating  CaCO3; 
hence  the  latter  is  employed  instead  of  the  former.  In 
what  case  would  SiO2  be  used  as  the  flux  ? 

Into  the  blast  furnace  are  put,  in  alternate  layers,  the 
fuel,  the  flux,  and  the  ore.  The  fire,  once  kindled,  is  kept 
burning  for  months  or  years.  Hot  air  is  driven  in  through 
the  tuyeres  (tweeri).  O  unites  with  C  of  the  fuel,  form- 
ing CO2  and  CO.  The  C  also  reduces  the  ore.  Fe2O3  +  3  C 
=-•?  CO  accomplishes  the  same  thing.  3CO  +  Fe2O3  =  ? 
The  intense  heat  fuses  CaO  and  SiO2  to  a  silicate  which, 
with  other  impurities,  forms  a  slag ;  this,  rising  to  the  sur- 
face of  the  molten  mass,  is  drawn  off.  The  iron  is  melted, 
falls  in  drops  to  the  bottom,  and  is  drawn  off  into  sand 
molds.  ,  See  Figure  47.  This  is  pig-iron.  It  contains  as 
impurities,  C,  Si,  S,  P,  Mn,  etc.  If  too  much  S  or  P  is  present 
in  an  ore,  it  is  worthless.  This  is  why  the  abundant  min- 
eral FeS2  cannot  be  used  as  a  source  of  iron.  From  the 
top  of  the  furnace  N,  CO,  CO2,  H2O,  etc.,  escape.  These 
gases  are  used  to  heat  the  air  which  is  forced  through  the 
tuyeres,  and  to  make  steam  in  boilers. 

267.  Steel.  —  The  manufacture  of  steel  and  wrought- 
iron  consists  in  removing  most  of  the  impurities  from  pig- 
iron.  It  will  be  seen  that  the  most  common  compounds  of 
C,  S,  Si,  and  P,  are  their  oxides,  and  these  are  for  the  most 
part  gases.  Hence  these  elements  are  removed  by  oxida- 
tion. 

Bessemer  steel  is  prepared  by  melting  pig-iron  and  blow- 
ing hot  air  through  it.  A  converter  (Fig.  48)  lined  with 
siliceous  sand,  and  holding  several  tons,  is  partially  filled 
with  the  molten  metal ;  blasts  of  hot  air  are  driven  into  it, 


IKON    AND    ITS    COMPOUNDS. 


157 


Fig.  48. 


and  the  C  and  other  impurities,  together  with  a  little  of 
the  Fe,  are  oxidized.  The  exact  moment  when  the  pro- 
cess has  gone  far  enough,  and  most  of  the  impurities  have 
been  removed,  is  indicated  by 
the  appearance  of  the  escaping 
flame.  It  usually  takes  from 
five  to  ten  minutes.  The  blast 
is  then  stopped,  and  the  metal 
has  about  the  composition  of 
wrought-iron ;  it  contains  some 
uncombiried  O.  A  white  pig-iron 
(spiegeleisen),  which  contains 
a  known  quantity  of  C  and  of 
Mn,  is  at  once  added.  Mn  re- 
moves part  of  the  extra  O,  and, 
though  it  remains,  does  not  in- 
jure the  metal.  The  C  is  '•  dissolved  "  by  the  Fe,  which  is 
then  run  into  molds  (ingots).  This  process,  the  Bessemer, 
invented  in  1856,  has  revolutionized  steel  manufacture. 
No  less  than  ten  tons  of  iron  have  been  converted  into 
steel,  in  five  minutes,  in  a  single  converter. 

268.    Wrought-iron. 

—  The  chemical  princi- 
ple involved  in  making 
wrought-iron  is  the  same 
as  that  in  making  steel, 
but  the  process  is  dif- 
ferent. Impurities  are 
burned  out  from  pig- 
iron  in  an  open  rever- 
beratory  furnace,  by  constantly  stirring  the  metal  in 
contact  with  air.  This  is  called  puddling.  A  reverbera- 


Fig.  49. 


158  IRON   AND   ITS   COMPOUNDS. 

tory  furnace  is  one  in  which  the  fuel  is  in  one  compart- 
ment, and  the  heat  is  reflected  downward  into  another, 
that  holds  the  substance  to  be  acted  upon  (Fig.  49). 

Steel  may  also  be  made  by  carburizing  wrought-iron.  Iron  and  char- 
coal are  packed  together  and  heated  for  days,  without  melting,  when  it  is 
found  that,  in  some  unknown  way,  solid  C  has  penetrated  solid  Fe.  The 
finer  kinds  of  steel  are  made  in  this  way,  but  they  are  very  expensive. 

Wrought-iron  may  also  be  made  directly  from  the  ore  in  an  open  hearth 
furnace,  with  charcoal.  This  was  the  original  mode. 

269.  Properties.  —  The  varying  properties  of  pig-iron, 
steel,  and  wrought-iron  are  due  in  part  to  the  proportion  of 
C  and  of  other  elements  present,  either  as  mixtures  or  as 
compounds,  and  in  part  to  other  causes  not  well  under- 
stood.    Wrought-iron  is  fibrous,  as  though  composed  of 
fine  wires,  and  hence  is  ductile,  malleable,  tough,  and  soft, 
and  cannot  be  hardened  or  tempered,  but  it  is  easily  welded. 
Pig-iron  is  crystalline,  and  so  is  not  ductile  or  malleable  ;  it 
is  hard  and  brittle,  and  cannot  be  welded.     On  account  of 
its  low  melting-point  it  is  generally  employed  for  castings. 
Steel  is  crystalline  in  structure,  and  when  suddenly  cooled 
from  red  heat  by  plunging  into  cold  water,  becomes  hard 
and  brittle.     The  tempering  can  be  varied  by  afterwards 
heating  to  any  required  degree,  indicated  by  the  color  of 
the  oxide  formed  on  the  exterior.     The  higher  tempera- 
tures give  the  softer  steel. 

270.  Salts  Of  Iron.  — Examine  FeSO4,  FeS,  FeS2. 

Fe  has  a  valence  of  2  or  4.  This  gives  rise  to  two  kinds 
of  salts,  ferrous  and  ferric,  as  in  FeCl2  and  Fe2Cl6.  The 
valence  of  Fe  in  ferric  salts  is  4.  See  page  40.  Ferrous 
sulphate  is  FeSO4;  ferric  sulphate,  Fe2(SO4)3.  Write  the 
symbols  for  ferrous  and  ferric  hydrate ;  for  the  oxides ; 
for  the  nitrates.  Write  the  graphic  symbols  for  each. 


IRON   AND   ITS   COMPOUNDS.  159 

271.  Colors.  —  The    characteristic    color    of    ferrous 
salts  is  green,  as  in  FeSO4.     These  salts  give  the  green 
color  to  the  chlorophyll  in  leaves  and  grass,  and  bottle 
glass  owes  its  green  color  to  ferrous  silicate.     Ferric  salts 
are  a  brownish  red,  as  shown  in  hematite  and  limonite, 
and  in  some  bottles.     Red  sandstone,  and  most  soils  and 
earths,  are  illustrations  of  this  coloring  action.     The  blood 
of  vertebrates  owes  its  color  to  ferric  salts.     Bricks  are 
made  from  a  greenish  blue  clay  in  which  iron  exists  in  the 
ferrous  state.     On  being  heated,  ferrous  salts  are  oxidized 
to  ferric,  and  their  color  is  changed  to  red.     Iron  rust  is 
hydrated  ferric  oxide,  Fe2O3  and  Fe2(OH)6. 

272.  Change  of  Valence. 

Experiment  122. — Dissolve  2&  of  iron  filings  in  diluted  HC1. 
Filter  or  pour  off  the  clear  liquid,  divide  it  into  two  parts,  and  add 
NH4OH  to  one  part  till  a  ppt.  occurs.  Notice  the  greenish  color  of 
Fe(OH)2.  Oxidize  the  other  part  by  adding  a  few  drops  of  HNO3 
and  boiling  a  minute.  Now  add  NH4OH,  and  observe  the  reddish 
color  of  the  ppt.,  Fe2(OH)6. 

Solutions  of  ferrous  salts  will  gradually  change  to  ferric, 
if  allowed  to  stand,  thus  showing  the  greater  stability  of 
the  latter.  In  changing  from  FeCl2  to  Fe2016  oxidation 
does  not  consist  in  adding  O,  but  in  increasing  the  nega- 
tive element  or  radical.  This  is  possible  only  by  chang- 
ing the  valence  of  Fe  from  2  to  4.  Hence  oxidation,  in  its 
larger  sense,  means  increasing  the  valence  of  the  positive 
element.  To  oxidize  FeSO4  is  to  make  it  Fe2(SO4)3,  chang- 
ing the  valence  of  Fe  as  before.  Reduction  or  deoxi- 
dation  diminishes  the  valence  of  the  positive  element. 
Illustrate  this  by  the  same  iron  salts.  Illustrate  it  by 
PbO  and  PbO2;  AuCl  and  AuCl3;  Sb2S3  and  Sb2S5.  In 
this  sense  define  an  oxidizing  agent.  A  reducing  agent. 


160  IRON    AND    ITS   COMPOUNDS. 

273.   Ferrous  Sulphate. 

Experiment  123.  —  Dissolve  a  few  iron  filings  in  dilute  H2SO4, 
and  slowly  evaporate  for  a  few  minutes.  Write  the  equation. 

Ferrous  sulphate,  green  vitriol,  or  copperas,  FeSO4  +  7  H2O,  is  the 
source  of  what  acid  ?  See  page  66.  It  is  also  one  of  the  ingredients  in 
many  writing  inks.  On  being  heated,  or  exposed  to  the  air,  it  loses  its 
water  of  crystallization  and  becomes  a  white  powder.  It  is  prepared  as 
above,  or  by  oxidizing  moistened  FeS2  by  exposure  to  the  air. 

Ferrous  sulphide,  protosulphide  of  iron,  FeS,  is  how  prepared  ?  See 
Experiment  6.  State  its  use.  See  Experiment  108.  It  also  occurs  native. 

Ferric  sulphide,  pyrite,  FeS2,  occurs  native  in  large  quantities.  What 
is  its  use  ?  See  page  65. 


CHAPTER   XLIX. 

LEAD  AND   TIN. 

LEAD. 

Examine  galena,  lead  protoxide  and  dioxide,  red-lead,  lead  carbo- 
nate, acetate,  and  nitrate.  Note  especially  the  colors  of  the  oxides,  the 
cubical  crystallization  and  cleavage  of  galena,  the  specific  gravity  of  the 
compounds,  the  softness  of  Pb,  and  the  tarnish,  Pb2O,  which  covers  it, 
if  long  exposed. 

274.  Distribution  of  Pb.  —  Pb  is  widely  distributed, 
occurring  as  PbS  and  PbCO3.     PbS,  galenite  or  galena,  is 
its  main  source.     By  heating  it  in  air,  SO2  is  formed,  and 
Pb  liberated  and  drawn  off. 

Pb  is  but  little  acted  on  by  cold  H2SO4,  unless  concen- 
trated. Describe  its  use  in  making  that  acid.  See  page  65. 
To  show  that  a  little  Pb  has  been  dissolved,  as  PbSO4,  in 
the  manufacture  of  that  acid,  perform  this  experiment. 

Experiment  124.  —  To  5CC  of  water  in  a  clean  t.t.  add  the  same  vol- 
ume of  H2SO4,  not  C.P.;  shake,  and  notice  any  fine  powder  sus- 
pended. PbSO4,  being  insoluble  in  water,  is  precipitated.  What  is 
the  test  for  Pb  ?  See  Experiment  109. 

275.  Poisonous  Properties.  —  Pb  is  very  flexible  and 
soft,  and  is  much  used  for  water  pipes.     In  moist  air  it  is 
soon  coated  with  suboxide,  Pb2O,  as  may  be  seen  by  ex- 
posing a  fresh  surface.     Some  portion  of  this  is  liable  to 
dissolve  in  water,  and,  as  all  soluble  salts  of  Pb  are  poison- 
ous, water  that  has  stood  in  pipes  should  not  be  used  for 


162  LEAD  AND   TIN. 

drinking.  Lead  is  employed  as  an  alloy  of  tin  for  cover- 
ing sheet-iron  in  "  terne  plate."  This  plate  is  rarely  used 
except  for  roofing.  The  "  bright  plate,"  used  for  tin  cans 
and  other  purposes,  scarcely  ever  contains  any  lead  except 
the  small  portion  in  solder.  In  soldering,  ZnCl2  is  em- 
ployed for  a  flux.  Sn,  Pb,  and  Zn  are  somewhat  soluble 
in  vegetable  acids.  If  citric  acid  be  present,  as  it  usually 
is,  citrates  of  these  metals  are  formed,  and  all  of  them  are 
poisonous.  The  action  is  far  more  rapid  after  opening  the 
can,  since  oxidation  is  hastened.  Hence  the  contents 
should  be  taken  out  directly  after  opening. 

Lead  poisons  seem  to  have  an  affinity  for  the  tissues  of  the  body,  and 
accumulate  little  by  little.  Painter's  colic  results  from  lead  poisoning. 
Epsom  salt,  or  other  soluble  sulphate,  is  an  antidote,  since  with  Pb  it 
makes  insoluble  PbS04. 

276.  Some  Lead  Compounds.  — Lead  salts  form  the  basis  of 
many  paints.  White  paint  is  a  mixture  of  PbC03  and  Pb(OH)2  suspended 
in  linseed  oil.  It  is  often  adulterated  with  BaS04,  ZnO,  CaC03.  Other 
lead  compounds  are  used  for  colored  paints.  The  two  chief  soluble  salts 
are  Pb(N03)2  and  lead  acetate,  Pb(C2H302)2. 

Red-lead,  Pb304,  and,  to  some  extent,  litharge,  PbO,  are  employed  in 
glass  manufacture.  Name  the  kind  of  glass  in  which  it  is  used,  describe 
its  manufacture,  and  write  a  symbol  for  lead  silicate.  What  is  the  charac- 
teristic of  lead  glass  ?  See  page  132. 

Experiment  125.  —  Put  a  small  fragment  of  Pb  on  a  piece  of 
charcoal,  and  blow  the  oxidizing  flame  against  it  for  some  time  with 
a  mouth  blow-pipe.  Note  the  color  of  the  coating  on  the  coal.  PbO 
has  formed. 

Experiment  126.  —  Dissolve  a  small  piece  of  lead  in  dilute  IINO3. 
Pour  off  the  solution  into  a  t.t.  and  add  HC1  or  other  soluble  chloride. 
Pb(NO3)2  +  2  HC1  =  ?  What  is  the  insoluble  product  ? 

Experiment  127.  —  Add  to  a  solution  of  Pb(C2H3O2)2  some  H2SO4< 
Give  the  reaction  and  the  explanation, 


LEAD  AND  TIN.  163 

TIN. 
Examine  cassiterite,  tin  foil,  "  terne  plate,"  "  bright  plate.'* 

277.  Sn  occurs  as  the  mineral  cassiterite,  tin  stone,  SnO2,  and  is  found 
in  only  a  few  localities,  as  Banca,  Malacca,  and  England.  It  does  not 
readily  tarnish,  and  is  used  to  cover  thin  plates  of  copper  and  iron.  Tin 
foil  is  generally  an  alloy  of  Pb  and  Sn. 

Sn  is  sometimes  a  dyad,  at  others  a  tetrad.  Write  symbols  for  its  two 
chlorides,  stannous  and  stannic,  also  for  its  sulphides  and  oxides. 


CHAPTER   L. 

COPPER,   MERCURY,   AND   SILVER. 
COPPER. 

Examine  native  copper,  chalcopyrite,  malachite,  azurite,  copper 
acetate,  copper  nitrate,  copper  sulphate. 

278.  Occurrence.  —  Copper  occurs  both  native  and  in 
many  compounds,  being  diffused  in  rocks  and,  in  minute 
quantities,  in  soils,  waters,  plants,  and  animals.      Spain, 
Chili,  and  the  United  States  are  the  chief  Cu  producing 
countries.      The  extensive  mines  of   Michigan  yield  the 
native  ore.     The  Calumet  and  Hecla  mine  alone  produces 
4,000,000  pounds  per  month.     The  most  abundant  com- 
pound of  Cu  is  chalcopyrite,  or  copper  pyrites,  CuFeS2. 
Malachite,  which  is  green,  and  azurite,  which  is  blue,  are 
carbonates,  the  former  being   used   for   ornamental   pur- 
poses. 

Cu  is,  next  to  Ag,  the  best  conductor  of  electricity  and 
heat  among  the  elements ;  it  is  very  ductile,  malleable,  and 
tenacious. 

Cu  has  two  valences,  1  and  2.  Symbolize  and  name  its  chlorides, 
iodides,  sulphides,  and  oxides.  Cupric  compounds,  as  a  rule,  are  more 
stable  than  cuprous. 

279.  Uses.  —  Thousands  of  t'ons  of  Cu  find  use  in  do- 
mestic utensils,  ocean  vessels,  electric  wires,  batteries,  and 
plating.     Name  the  chief  alloys  of  Cu  and  their  uses.     See 
page  136. 


MERCURY   AND   SILVER. 


165 


How  may  CuS  be  obtained  ?  See  Experiment  7.  Cu20,  cuprous  oxide,  is 
used  to  color  glass  red.  CuS04  is  employed  in  calico-printing,  electric 
batteries,  etc.  It  is  called  blue  vitriol. 

Paris  green,  used  for  killing  potato-beetles,  is  composed  chiefly  of 
copper  arsenite.  Write  the  symbol  for  this  compound.  All  soluble  salts 
of  Cu  are  poisonous ;  hence  care  should  be  taken  not  to  bring  any  acid 
in  contact  with  copper  vessels  of  domestic  use.  With  acetic  acid,  what 
would  be  formed  ? 

MERCURY  AND   ITS   COMPOUNDS. 

Examine  cinnabar,  vermilion,  mercury,  red  oxide,  mercurous  and 
mercuric  chloride. 

280.  Cinnabar,  HgS,  is  practically  the  only  source  of  mercury  — 
quicksilver.     Austria,  Spain,  and  California  contain  nearly  all  the  mines. 
In  these   mines   the  metal  also  occurs  native  to  a  small  extent.     It  is 
the  only  commonly  occurring  metal  that  is  liquid  at  ordinary  tempera- 
tures ;   it  solidifies  at  about  —  40°.     What  other  common  liquid  element  ? 
See  page  12.     Hg  is  reduced  from  the  ore  by  Fe,  Hg  being  distilled  over 
and  collected  in  water.    Heat  regularly  expands  the  metal. 

281.  Uses.  —  For  uses  see  Reduction  of  Ag   and  Au,  pages  165 
and  170;  amalgams,  page  137;  laboratory  work,  page  68.     It  is  also  em- 
ployed for  thermometers  and  barometers,  and  as  the  source  of  the  red 
pigment  vermilion,  which  is  artificial  HgS. 

Compare  the  vapor  density  and  the  atomic  weight  of  Hg,  and  explain. 
See  page  12.  Hg  is  either  a  monad  or  a  dyad.  Symbolize  its  ous  and  ic  ox- 
ides and  chlorides.  Which  of  the  following  are  ic  salts,  and  which  are  ous, 
and  why  ?  HgN03,  Hg(N08)2,  HgCl,  HgCl2?  Calomel,  HgCl  or  Hg2Cl2, 
used  in  medicine,  and  corrosive  sublimate,  HgCl2,  are  illustrations  of  the  ous 
and  ic  salts.  The  former  is  insoluble,  the  latter  soluble.  All  soluble  com- 
pounds of  Hg  are  virulent  poisons,  for  which  the  antidote  is  the  white  of 
egg,  albumen.  With  it  they  coagulate  or  form  an  insoluble  mass. 

SILVER  AND   ITS  COMPOUNDS. 

282.  Occurrence  and  Reduction.  —  Silver  is  found  uncom- 
bined,  and  combined,  as  Ag2S,  argenite,  and  AgCl,  horn  silver.     It  occurs 
usually  with  galena,  PbS.      It  is  abundant  in  the  Western  States,  Mex- 
ico, and  Peru.      Silver  is   separated  from   galena  by  melting  the  two 
metals.      As    they  slowly  cool,  Pb  crystallizes,  and  is  removed  by  a 


166  MERCURY  AND  SILVER. 

sieve,  while  Ag  is  left  in  the  liquid  mass.  The  principle  is  much  like 
crystallizing  NaCl  from  solution  and  leaving  behind  the  salts  of  Mg,  etc., 
in  the  mother  liquor.  When,  by  repeating  the  process,  most  of  the  Pb  is 
eliminated,  the  rest  is  oxidized  by  heating  in  the  air.  Pb  +  O  =  PbO.  Ag 
does  not  oxidize,  and  is  left  in  the  metallic  state. 

Another  mode  of  reduction  is  to  change  the  silver  salt  to  its  chloride, 
and  then  remove  the  Cl  with  Fe.  Roasting  with  NaCl  makes  the  first 
change,  2  NaCl  +  Ag.2S  =  Na2S  +  2  AgCl,  and  with  Fe  the  second,  2  AgCl 
-f  Fe=  FeCl2  +  2  Ag.  Ag  is  separated  from  the  other  products  by  adding 
Hg,  with  which  it  forms  an  amalgam.  By  distilling  this,  Hg  passes  over 
and  Ag  remains.  This  is  the  amalgamating  process. 

283.  Salts  of  Silver  are  much  employed  in  organic  chemistry, 
and  AgCl,  AgBr,  and  AgN03  are  used  in  photography.  AgNO3  is  a  sol- 
uble, colorless  crystal,  and  is  the  basis  of  the  silver  salts.  It  blackens  when 
in  contact  with  organic  matter.  Stains  on  a  photographer's  hands  are  due 
to  this  substance,  and  the  use  of  AgN03  in  indelible  inks  depends  on  the 
same  property.  This  may  be  due  to  a  reduction  of  AgNO3  to  Ag4O. 
Stains  can  be  removed  from  the  skin  or  from  linen  by  a  solution  of  KI,  or 
of  CuCl2  followed  by  sodium  hyposulphite.  Lunar  caustic  is  made  by 
fusing  AgN03  crystals,  and  is  used  for  cauterizing  (burning)  the  flesh. 
Much  AgCN  finds  use  in  electroplating. 

Experiment  128.  —  Put  5CC  AgNO3  solution  in  each  of  three  t.t. 
To  the  first  add  3CC  HC1,  to  the  second  3CC  NaCl  solution,  and  to  the 
third  3CC  KBr  solution.  Write  the  reaction  for  each  case,  and  notice 
that  the  first  two  give  the  same  ppt.,  as  in  fact  any  soluble  chloride 
would.  Filter  the  second  and  third,  on  separate  filter  papers,  and 
expose  half  the  residue  to  direct  sunlight,  observing  the  change  of 
color  by  occasionally  stirring.  Solar  rays  reduce  AgCl  and  AgBr,  it 
is  thought,  to  Ag2Cl  and  Ag2Br.  Try  to  dissolve  the  other  half  in 
Na2S2O3,  sodium  thiosulphate  solution'.  This  experiment  illustrates 
the  main  facts  of  photography . 


CHAPTER   LI. 

PHOTOGRAPHY. 

284.  Descriptive.  —  The  silver  halogens,  AgCl,  AgBr,  Agl, 
are  very  sensitive  to  certain  light  rays.  Red  rays  do  not  affect  them; 
hence  ruby  glass  is  used  in  the  "  dark  room." 

Photography  involves  two  processes.  The  negative  of  the  picture  is 
first  taken  upon  a  prepared  glass  plate,  and  the  positive  is  then  printed  on 
prepared  paper.  The  negative  shows  the  lights  and  shades  reversed, 
while  the  positive  gives  objects  their  true  appearance. 

Few  photographers  now  make  their  own  plates,  these  being  prepared  at 
large  manufactories.  The  glass  is  there  covered  on  one  side  with  a  white 
emulsion  of  gelatine  and  AgBr,  making  what  are  called  gelatine-bromide 
plates.  This  is  done  in  a  room  dimly  lighted  with  ruby  light.  The  plates 
are  dried,  packed  in  sealed  boxes,  and  thus  sent  to  photographers.  The 
artist  opens  them  in  his  dark  room,  similarly  lighted,  inserts  the  plates 
in  holders,  film  side  out,  covers  with  a  slide,  adjusts  to  the  camera,  pre- 
viously focused,  and  makes  the  exposure  to  light.  The  time  of  exposure 
varies  with  the  kind  of  plate,  the  lens,  and  the  light,  from  several  seconds, 
minutes,  or  hours,  to  ^  part  of  a  second  in  some  instantaneous  work.  In 
the  dark  room  the  plates  are  removed  and  can  be  at  once  developed,  or 
kept  for  any  time  away  from  the  light.  No  change  appears  in  the  plate 
until  development,  though  the  light  has  done  its  work. 

To  develop  the  plate,  it  is  put  into  a  solution  of  pyrogallic  acid,  the 
developer,  and  carbonate  of  sodium,  the  motive  power  in  the  process. 
Other  developers  are  often  used.  The  chemical  action  here  is  somewhat 
obscure,  but  those  parts  of  the  plates  which  were  affected  by  the  light  are 
made  visible,  a  part  of  the  Ag2Br  being  reduced  to  Ag  by  the  affinity 
which  sodium  pyrogallate  has  for  Br.  Ag2Br  =  2  Ag  +  Br.  Br  is  dis- 
solved and  Ag  is  deposited.  When  the  rather  indistinct  image  begins  to 
fade  out,  the  plate  is  dipped  for  a  minute  into  a  solution  of  alum  to  harden 
the  gelatine  and  prevent  it  from  peeling  off  (frilling).  It  is  finally  soaked 
in  a  solution  of  sodium  thiosulphate  (hyposulphite  or  hypo),  Na2S2O3. 
This  removes  the  AgBr  that  the  light  has  failed  to  reduce.  The  process 


168  PHOTOGRAPHY. 

is  called  fixing,  as  the  plate  may  thereafter  be  exposed  to  the  light  with 
impunity.  It  must  be  left  in  this  bath  till  all  the  white  part,  best  seen  on 
the  back  of  the  plate,  disappears.  2  AgBr  + 3Na2S203=  Ag.2Na4(S2O3) 
+  2  NaBr.  Both  products  are  dissolved.  It  is  then  thoroughly  washed. 
Any  dark  objects  become  light  in  the  negative,  and  vice  versa.  Why  ? 

For  the  positive,  the  best  linen  paper  is  covered  on  one  side  with 
albumen,  soaked  in  NaCI  solution,  dried,  and  the  same  side  laid  on  a  solu- 
tion of  AgNO3.  What  reaction  takes  place  ?  What  is  deposited  on  the 
paper,  and  what  is  dissolved  ?  This  sensitized  paper,  when  dry,  is  placed 
over  a  negative,  film  to  film,  and  exposed  in  a  printing  frame  to  direct 
sunlight  till  much  darker  than  desired  in  the  finished  picture.  What  is 
dark  in  the  negative  will  be  light  in  the  positive.  Why  ?  The  reducing 
action  of  sunlight  is  similar  to  that  in  the  negative.  Explain  it. 

After  printing,  the  picture  is  toned  and  fixed.  Toning  consists  in  giv- 
ing it  a  rich  color  by  replacing  part  of  the  Ag2Cl  with  gold  from  a  neutral 
solution  of  AuCl3.  3  Ag2Cl  +  AuCl3  =  6  AgCl  +  Au.  Fixing  removes  the 
unaffected  AgCl,  as  in  the  negative,  the  same  substance  being  used.  De- 
scribe the  action.  2  AgCl  +  3  Na2S2O3  =  Ag2Na4(S2O3)3  +  2  NaCI.  Both 
the  positive  and  the  negative  must  be  well  washed  after  each  process, 
particularly  after  the  last.  The  picture  is  then  ready  for  mounting.  In 
fine  portrait  work  both  the  negative  and  the  positive  are  retouched.  This 
consists  in  removing  blemishes  with  colored  pencils  or  India  ink. 

The  negative.  —  No.  1.  Dissolve:  sulphite  soda  crystals,  2  oz.  (57s)  in 
8  oz.  (236CC)  water  (distilled) ;  citric  acid,  60  grains  (4s)  in  £  oz.  (15CC) 
water;  bromide  ammonium,  25  grains  (!£«)  in  \  oz.  water;  pyrogallic 
acid,  1  oz.  (28s)  in  3  oz.  (90CC)  water.  After  dissolving,  mix  in  the  order 
named,  and  filter.  No.  2.  Dissolve :  sulphite  soda,  2  oz.  (578)  in  4  oz. 
(118CC)  water;  carbonate  potash,  4  oz.  (113g)  in  8  oz.  (236CC)  water.  Dis- 
solve separately,  mix,  and  filter.  To  develop  plates,  mix  1  dram  (3§cc)  of 
No.  1  and  1  dram  of  No.  2  with  2  oz.  (60CC)  'water.  Cover  the  plate  with 
the  mixture,  and  leave  as  long  as  the  picture  increases  in  distinctness. 
Remove,  wash,  and  put  it  into  a  saturated  solution  of  alum  for  a  minute 
or  two,  then  wash  and  put  it  into  a  half-saturated  solution  of  hypo.  Leave 
till  no  white  AgCl  is  seen  through  the  back  of  the  plate.  Wash  it  well. 

The  positive.  —  1.  Dissolve  30  grains  (28)  pure  gold  chloride  in  15  oz. 
(450°°)  water.  This  forms  a  stock  solution.  2.  Make  a  saturated  solution 
of  borax.  3.  Prepare  a  toning  bath  by  adding  J  oz.  (15CC)  of  the  gold 
chloride  solution  and  1  oz.  (30CC)  of  the  borax  solution  to  7  oz.  (210CC)  water. 
After  printing  the  picture,  wash  it  in  3  or  4  waters,  put  it  into  the  toning 
bath,  and  leave  it  till  considerably  darker  than  desired ;  wash,  and  put  it 
for  15  minutes  into  a  hypo  solution  that  has  been,  after  saturation,  diluted 
with  3  or  4  volumes  of  water.  Then  wash  repeatedly. 


CHAPTER   LIT. 
PLATINUM  AND   GOLD. 

PLATINUM. 

Examine  platinum  foil  and  wire. 

285.  Platinum  is  much  rarer  than  gold,  and  is  about  two-thirds 
as  costly  as  the  latter.     It  is  found  alloyed  with  other  metals,  as  Au,  and 
is  obtained  from  sand,  in  which  it  occurs,  by  washing.     Aqua  regia  is  the 
only  acid  which  dissolves  it,  and  the  action  is  much  slower  than  with  Au. 
Ft  is  one  of  the  heaviest  metals,  having  a  specific  gravity  three  times  that 
of  Fe,  or  twenty-one  and  a  half  times  that  of  water.     Its  fusing-point  is 
about  1600°,  or  just  below  the  temperature  of  the  oxy-hydrogen  flame. 
Like  Au  it  has  little  affinity  for  other  elements,  but  alloys  with  many 
metals.     Ft  is  so  tenacious  that  it  can  be  drawn  into  wire  invisible  to  the 
naked  eye,  being  drawn  out  in  the  center  of  a  silver  wire,  which  is  after- 
wards dissolved  away  from  the  Ft  by  HN03.    Noting  its  valences,  2  and  4, 
write  the  symbols  for  the  ous  and  ic  chlorides  and  oxides. 

286.  Uses.  —  Ft  is  much  used  in  chemistry  in  the  form  of  foil, 
wire,  and  crucibles.    On  what  properties  does  this  use  depend  ?    Describe 
its  use  in  making  H2S04.    See  page  65. 

FtCl4  is  made  by  dissolving  Ft  in  aqua  regia,  and  evaporating  the 
liquid.  On  heating  FtCl4,  half  of  its  Cl  is  given  up,  leaving  FtCl2.  If  it 
be  still  more  strongly  heated,  the  Cl  all  passes  off,  leaving  spongy  Ft.  By 
fusing  this  in  the  oxy-hydrogen  flame,  ordinary  Ft  is  obtained.  Spongy 
Ft  has  a  remarkable  power  of  absorbing,  or  occluding,  O  without  uniting 
with  it.  This  O  it  gives  up  to  some  other  substances,  and  thus  becomes 
indirectly  an  oxidizing  agent.  What  other  element  has  this  property  of 
occluding  gases  1 

GOLD. 

Examine  auriferous  quartz,  gold  chloride,  yellow  and  ruby  glass  col- 
ored with  gold. 


170  PLATINUM  AND  GOLD. 

287.  Gold  is  rarely  found  combined,  and  has  small  affinity  for 
other  elements,  though  forming  alloys  with  Cu,  Ag,  and  Hg.  Its  source 
is  usually  either  quartz  rock,  called  auriferous  quartz,  or  sand  in  placer 
mines.  The  element  is  widely  distributed,  occurring  in  minute  quantities 
in  most  soils,  sea  water,  etc.  California  and  Australia  are  the  two  greatest 
gold-producing  countries.  That  from  California  has  a  light  color,  due  to 
a  slight  admixture  of  Ag.  Australian  gold  is  of  a  reddish  hue,  due  to 
an  alloy  of  Cu.  Gold-bearing  quartz  is  pulverized,  and  treated  with  Hg  to 
dissolve  the  precious  metal,  which  is  then  separated  from  the  alloy  by 
distillation.  Compare  this  with  the  preparation  of  Ag. 

Such  is  the  malleability  of  Au  that  it  has  been  hammered  into  sheets 
not  over  one-millionth  of  an  inch  thick ;  it  is  then  as  transparent  as  glass. 
Gold  does  not  tarnish  or  change  below  the  melting-point.  On  account  of 
its  softness  it  is  usually  alloyed  with  Cu,  sometimes  with  Ag.  Pure  gold 
is  twenty-four  carats  fine.  Eighteen  carat  gold  has  eighteen  parts  Au  and 
six  Cu.  Gold  coin  has  nine  parts  Au  to  one  part  Cu.  The  most  important 
compound  is  AuCl3.  Describe  a  use  of  it.  See  page  168.  This  metal  is 
much  employed  in  electroplating,  and  somewhat  in  coloring  glass. 


CHAPTER   LIII. 

CHEMISTRY  OF  ROCKS. 

288.  Classification.  —  Rocks   may  be  divided,  accord- 
ing to  their  origin,  into  three  classes:    (1)  Aqueous  rocks. 
These  have  been  formed  by  deposition  of  sedimentary  ma- 
terial, layer  by  layer,  on  the  bottoms  of  ancient  oceans, 
lakes,  and  rivers,  from  which  they  have  gradually  been 
raised,  to  form  dry  land.     (2)  Eruptive  or  volcanic  rocks. 
These  have  been  forced,  as  hot  fluids,  through  rents  and 
fissures  from   the  interior  of  the  earth.      (3)   Metamor- 
phic  rocks.     These,  by  the  combined  action  of  heat,  pres- 
sure, water,  and  chemical  agents,  have  been  crystallized 
and  chemically  altered.     The  rocks  of  the  first  class,  such 
as  chalk,  limestone,  shale,  and  sandstone,  are  distinguished 
by  the  existence  of  fossils  in.  them,  or  by  the  successive 
layers  of  the  material  which  goes  to  make  up  their  struc- 
ture and  to  give  them  a  stratified  appearance.    The  rocks  of 
the  second  class  are  recognized  by  their  resemblance  to  the 
products  of  modern  volcanoes  and  their  non-stratified  ap- 
pearance.    Rocks  of  the  third  class  are  composed  of  crys- 
tals, which,  though  often  very  minute,  are  minerals  having 
a  definite  chemical  composition.     Examples  of  the  third 
class  are  gneiss,  slate,  schist,  and  marble.     The  last  two 
classes  abound  on  the  Eastern  sea-board,  while  the  interior 
of  our  continent  is  composed  almost  exclusively  of  strati- 
fied sedimentary  rocks. 

289.  Composition.  —  Rocks    are    not    definite    com- 
pounds, but  variable  mixtures  of  minerals.     Some,  how- 


172  CHEMISTRY  OF  BOCKS. 

ever,  are  tolerably  pure,  as  limestone  (CaCO3)  and  sand- 
stone. 

Granite  is  mainly  made  up  of  three  minerals,  —  quartz, 
feldspar,  and  mica.  Quartz,  when  pure,  is  SiO2.  Feldspar 
is  a  mixed  silicate  of  K  and  Al,  and  often  several  other 
metals,  K2Al2Si6O16  (=K2O,  A12O3,  6  SiO2)  symbolizing 
one  variety,  while  a  variety  of  mica  is  H8Mg5Fe7Al2Si3Oi8. 

The  pupil  should  learn  to  distinguish  the  different  minerals  in  granite. 
Quartz  is  glassy,  mica  is  in  scales,  usually  white  or  black,  and  feldspar 
is  the  opaque  white  or  red  mineral. 

290.  Importance    of    Siliceous    Rocks.  —  Slate    and 
schist  are  also  mixed  silicates.     Pure  sandstone  is  SiO2, 
the  red  variety  being  colored  by  iron. 

Igneous  rocks  are  always  siliceous.  Obsidian  is  a 
glassy  silicate.  A  mountain  of  very  pure  glass,  obsidian, 
two  hundred  feet  high,  has  lately  been  found  in  the  Yellow- 
stone region.  We  see  how  important  Si  is,  in  the  com- 
pounds SiO2  and  the  silicates,  as  a  constituent  of  the  ter- 
restrial crust.  Limestone  is  the  only  extensive  rock  from 
which  it  is  absent.  Always  combined  with  O,  it  is, 
next  to  the  latter,  the  most  abundant  of  elements.  Sili- 
cates of  Al,  Fe,  Ca,  K,  Na,  and  Mg  are  most  common,  and 
these  metals,  in  the  order  given,  rank  next  in  abundance. 

291.  Soils.  —  Beds  of  sand,  clay,  etc.,  are  disintegrated 
rock.     Sand  is  chiefly  SiO2;   clay  is  decomposed  feldspar, 
slatestone,  etc.     Soils  are  composed  of  these  with  an  added 
portion  of  carbonaceous  matter  from  decaying  vegetation, 
which  imparts  a  dark  color.     The  reddish  brown  hue  so 
often  observed  in  soils  and  rocks  results  from  ferric  salts. 

292.  Minerals,  of  which  nearly  1000  varieties  are  now 
known,  may  be   simple   substances,  as  graphite  and  sul- 


CHEMISTRY   OF    ROCKS.  173 

phur,  or  compounds,  as  galena  and  gypsum.  Only  seven 
systems  of  crystallizations  are  known,  but  these  are  so 
modified  as  to  give  hundreds  of  forms  of  crystals.  See 
Physics,  page  21.  A  given  chemical  substance  usually  oc- 
curs in  one  system  only,  but  we  saw  in  the  case  of  S  that 
this  was  not  always  true. 

Crystals  of  some  substances  deliquesce,  or  take  water  from  the  air,  and 
thus  dissolve  themselves.  See  page  142.  Some  compounds  cannot  exist 
in,  the  crystalline  form  without  a  certain  percentage  of  water.  This  is 
called  "  water  of  crystallization  " ;  if  it  passes  into  the  air  by  evaporation, 
the  crystal  crumbles  to  a  powder,  and  is  then  said  to  effloresce.  See  page 
139. 

293.  The  Earth's  Interior.  —  We  are  ignorant  of  the 
chemistry  of  the  earth's   interior.      The    deepest   boring 
is  but  little  more  than  a  mile,  and  volcanic  ejections  proba- 
bly come  from  but  a  very  few  miles  below  the  surface. 
The  specific  gravity  of  the  interior  is  known  to  be  more  than 
twice  that  of  the  surface  rock.      From  this  it  has  been 
imagined  that  towards  the  center  heavy  metals  like  Fe  and 
Au  predominate;  but  this  is  by  no  means  certain,  since 
the  greater  pressure  at  the  interior  would  cause  the  spe- 
cific gravity  of  any  substance  to  increase. 

294.  Percentage  of  Elements.  —  Compute  the  percentage 
of  0  in  the  following  rocks,  which  compose  a  large  proportion  of  the 
earth's  crust :  SiO2,  Al2Si04,  CaC03.     Find  the  percentage  of  0  in  pure 
water.     In  air.      Taking  cellulose,  C18H30O15,  as  the  basis,  find  the  per- 
centage of  O  in  vegetation. 

An  estimate,  based  on  Bunsen's  analysis  of  rocks,  of  the  chief  ele- 
ments in  the  earth's  crust,  is  as  follows :  — 


O,  46  per  cent. 
Si,  30 
Al,  8 
Fe,  6 


Ca,    3  per  cent. 
Na,   2 
K,     2 
Mg,  1         - 


More  than  half  the  elements  are  known  to  exist  in  sea-water,  and  the 
rest  are  thought  to  be  there,  though  dissolved  in  sirch  small  quantity  as  to 
elude  detection.  What  four  are  found  in  the  atmosphere  ? 


ESITF! 


CHAPTER   LIV, 

ORGANIC    CHEMISTRY. 

295.  General   Considerations.  —  Inorganic   chemistry 
is   the    chemistry    of    minerals,    or    unorganized    bodies. 
Organic  chemistry  was  formerly  defined  as  the  chemistry 
of  the  compounds  found  in  plants  and  animals ;  but  of  late 
it  has  taken  a  much  wider  range,  and  is  now  denned  as 
the  chemistry  of  the  C  compounds,  since  C  is  the  nucleus 
around  which  other  elements  centre,  and  with  which  they 
combine  to  form  the  organic  substances.     New  organic 
compounds  are  constantly  being  discovered  and  synthe- 
sized, so  that  nearly  100,000  are  now  known.     The  mole- 
cule of  organic  matter  is  often  very  complex,  sometimes 
containing  hundreds  of  atoms. 

In  organic  as  in  inorganic  chemistry,  atoms  are  bound 
together  by  chemical  affinity,  though  it  was  formerly  sup- 
posed that  an  additional  or  vital  force  was  instrumental  in 
forming  organic  compounds.  For  this  reason  none  of 
these  substances,  it  was  thought,  could  be  built  up  in 
the  laboratory,  although  many  had  been  analyzed.  In 
1828  the  first  organic  compound,  urea,  was  artificially 
prepared,  and  since  then  thousands  have  been  synthe- 
sized. They  are  not  necessarily  manufactured  from  or- 
ganic products,  but  can  be  made  from  mineral  matter. 

296.  Molecular  Differences.  —  Molecules   may  differ 
in  three  ways:    (1)  In  the  kind  of  atoms  they  contain. 
Compare   CO2  and   CS2.     (2)  In   the  number  of  atoms, 


ORGANIC   CHEMISTRY.  175 

Compare  CO  and  CO2.  (3)  In  the  arrangement  of  atoms, 
i.e.  the  molecular  structure.  Ethyl  alcohol  and  methyl 
ether  have  the  same  number  of  the  same  elements,  C2H6O, 
bu-t  their  molecular  structure  is  not  the  same,  and  hence 
their  properties  differ. 

Qualitative  analysis  shows  what  elements  enter  into  a 
compound ;  quantitative  analysis  shows  the  proportion  of 
these  elements;  structural  analysis  exhibits  molecular 
structure,  and  is  the  branch  to  which  organic  chemists  are 
now  giving  particular  attention. 

A  specialist  often  works  for  years  to  synthesize  a  series 
of  compounds  in  the  laboratory. 

297.  Sources.  —  Some  organic  products  are  now  made 
in  a  purer  and  cheaper  form  than  Nature  herself  prepares 
them.  Alizarine,  the  coloring  principle  of  madder,  was 
until  lately  obtained  only  from  the  root  of  the  madder 
plant;  now  it  is  almost  wholly  manufactured  from  coal- 
tar,  and  the  manufactured  article  serves  its  purpose  much 
better  than  the  native  product.  Ten  million  dollars' 
worth  is  annually  made,  and  Holland,  the  home  of  the 
plant,  is  giving  up  madder  culture.  Artificial  naphthol- 
scarlet  is  abolishing  the  culture  of  the  cochineal  insect. 
Indigo  has  also  been  synthesized.  Certain  compounds 
have  been  predicted  from  a  theoretical  molecular  struc- 
ture, then  made,  and  afterwards  found  to  exist  in  plants. 
Others  are  made  that  have  no  known  natural  existence. 
The  source  of  a  large  number  of  artificial  organic  products 
is  coal-tar,  from  bituminous  coal.  Saccharine,  a  com- 
pound with  two  hundred  and  eighty  times  the  sweetening 
power  of  sugar,  is  one  of  its  latest  products.  Wood, 
bones,  and  various  fermentable  liquids  are  other  sources 
of  organic  compounds. 


176  ORGANIC    CHEMISTKY. 

298.  Marsh-Gas  Series.  —  The  chemistry  of  the  hydro- 
carbons depends  on  the  valence  of  C,  which,  in  most  cases, 
is  a  tetrad.  Take  successively  1,  2,  and  3  C  atoms,  satu- 
rate with  H,  and  note  the  graphic  symbols :  — 

H  H    H  H     H    H 

I  II  III 

H-C-H,  orCH4.  H-C-C-H,  or?  H-0-C-C-H,  or   ? 

I  II  III 

H  H    H  H     H    H 

Write  the  graphic  and  common  symbols  for  4,  5,  and  6  C 
atoms,  saturated  with  H.  Notice  that  the  H  atoms,  are 
found  by  doubling  the  C  atoms  and  adding  2.  Hence  the 
general  formula  for  this  series  would  be  CnH2n+2.  Write 
the  common  symbol  for  C  and  H  with  ten  atoms  of  C ; 
twelve  atoms ;  thirteen.  This  series  is  called  the  marsh- 
gas  series.  The  first  member,  CH4,  methane,  or  marsh 
gas,  may  be  written  CH3H,  methyl  hydride,  CH3  being 
the  methyl  radical.  C2H6,  ethane,  the  second  one,  is  ethyl 
hydride,  C2H5H.  Theoretically  this  series  extends  without 
limit ;  practically  it  ends  with  C^Hya. 

In  each  successive  compound  of  the  following  list,  the  C  atoms 
increase  by  unity.  Give  the  symbols  and  names  of  the  compounds, 
and  commit  the  latter  to  memory :  — 

Boiling-point. 

1.  CH4  methane,  or  CH3H,  methyl  hydride,  gas. 

2.  C2H6  ethane,          C2H5H,  ethyl  hydride,  " 

3.  C3H8  propane,        C3H7H,  propyl  hydride,  " 

4.  ?  butane,          ?  ?  1° 

5.  ?  pentane         ?  ?  38° 

6.  ?  hexane,          ?  ?  70° 

7.  ?  heptane,        ?  ?  98° 

8.  ?  octane,  ?  ?  125° 

9.  ?  nonane,         ?  ?  148° 
10.  ?  dekane,         *  ?  171° 

Note  a  successive  increase  of  the  boiling-point  of  the  compounds. 
Crude  petroleum  contains  these  hydro-carbons  up  to  10.  Petroleum 


ORGANIC  CHEMISTRY.  177 

issues  from  the  earth,  and  is  separated  into  the  different  oils  by 
fractional  distillation  and  subsequent  treatment  with  H2SO4,  etc. 
llhigoline  is  mostly  5  and  6 ;  gasoline,  6  and  7 ;  benzine,  7 ;  naphtha, 
7  and  8 ;  kerosene,  9  and  10.  Below  10  the  compounds  are  solids. 
None  of  those  named,  however,  are  pure  compounds.  Explosions  of 
kerosene  are  caused  by  the  presence  of  the  lighter  hydro-carbons, 
as  naphtha,  etc.  Notice  that,  in  going  down  the  list,  the  proportion 
of  C  to  H  becomes  much  greater,  and  the  lower  compounds  are  the 
heavy  hydro-carbons.  To  them  belong  vaseline,  paraffine,  asphaltum, 
etc. 

299.  Alcohols.  —  The  following  replacements  will  show 
how  the  symbols  for  alcohols,  ethers,  etc.,  are  derived  from 
those  of  the  marsh-gas  series.  Notice  that  these  symbols 
also  exhibit  the  molecular  structure  of  the  compound. 
In  CH3H  by  replacing  the  last  H  with  the  radical  OH, 
we  have  CH3OH,  methyl  hydrate.  By  a  like  replace- 
ment C2H5H  becomes  C2H5OH,  ethyl  hydrate.  These 
hydrates  are  alcohols,  and  are  known  as  methyl  alcohol, 
ethyl  alcohol,  etc.  The  common  variety  is  C2H5OH.  How 
does  this  symbol  differ  from  that  for  water,  HOH?  No- 
tice in  the  former  the  union  of  a  positive,  and  also  of  a 
negative,  radical. 

Complete  the  table  below,  making  a  series  of  alcohols,  by  substitu- 
tions as  above  from  the  previous  table. 

1.  CH3OH,  methyl  hydrate,  or  methyl  alcohol. 

2.  C2H5OH,  ethyl  hydrate,  or  ethyl  alcohol. 

3.  ?  ?  ? 

4.  ?  ?  ? 

5.  ?  ?  ? 
Continue  in  like  manner  to  10. 

The  graphic  symbol  for  CH3OH  is  — 

H 

I 
H-C-OH; 

I 
H 


178  ORGANIC    CHEMISTRY. 

for  C2H5OH  it  is 

H    H 
I      I 
H-C-C-OH. 

I       I 
H    H 

Write  it  for  the  next  two. 

300.  Ethers.  —  Another  interesting  class  of  compounds  are  the 
oxides  of  the  marsh-gas  series.      In  this  series,  O  replaces  H.     CHSH 
becomes  (CH3)2O,  and  C2H5H  becomes  (C2H5)2O.     Why  is  a  double 
radical    taken?      These   oxides    are    ethers,   common    or  sulphuric 
ether  being   (C2H5).2O.     Complete  this  table,  by  substituting  O  in 
place  of  H,  in  the  table  on  page  176. 

1.  (CH3)20,  methyl  oxide,  or  methyl  ether. 

2.  (C2H5)20,  ethyl  oxide,  or  ethyl  ether. 

3.  ?  ?  ? 

4.  ?  ?  ? 

5.  etc.  ?  ?  ? 

Graphically  represented  the  first  two  are  :  — 

H  H  H     H  H     H 

II  I       I  I       I 

(1)     H-C-O-C-H.  (2)     H-C-C-O-C-C-H. 
II  I       I  I       I 

H  H  H    H  H    H 

301.  Substitutions.  —  A  large  number  of  other  substi- 
tutions can  be  made  in  each  symbol,  thus  giving  rise  to  as 
many  different  compounds. 

In  CH4,  by  substituting -3  Cl  for  3  H,  — 

H  Cl 

I  I 

H  —  C  —  H     becomes     H  —  C  —  Cl,  or  CHC13,  the  symbol  for  chloroform. 

H  Cl 

Replace  successively  one,  two,  and  four  atoms  with  Cl, 
and  write  the  common  symbols.  Make  the  same  changes 
with  Br.  For  each  atom  of  H  in  CH4  substitute  the  radi- 
cal CH3,  giving  the  graphic  and  common  formulae.  Also 
substitute  C2H5.  Are  these  radicals  positive  or  negative  ? 


ORGANIC   CHEMISTRY.  179 

From  the  above  series  of  formulse,  of  which  CH4  is  the 
basis,  are  derived,  in  addition  to  the  alcohols  and  ethers, 
the  natural  oils,  fatty  acids,  etc. 

302.  defines.  —  A  second   series  of  hydro-carbons  is 
represented  by  the  general  formula  CnH2n.    The  first  mem- 
ber of  this  series  is  C2H4,  or,  graphically,  — 

H  H 
I  I 
c  =  c. 

I      I 

H     H 

Compare  it  with  that  for  C2H6,  in  the  first  series,  noting 
the  apparent  molecular  structure  of  each. 

H          H 

I  I 

C  =  C  —  C  —  H,  or  C3H6  is  the  second  member. 

A  4  A 

Write  formulae  for  the  third  and  fourth  members. 

Write  the  common  formulae  for  the  first  ten  of  this  series. 
This  is  the  olefiant-gas  series,  and  to  it  belong  oxalic  and 
tartaric  acids,  glycerin,  and  a  vast  number  of  other  com- 
pounds, many  of  which  are  derived  by  replacements. 

303.  Other  Series.  —  In  addition  to  the  two  series  of 
hydro-carbons  above  given,  CnH2n-f-2  and  CJtl^,  other  se- 
ries are  known  with  the  general  formulae  CnH2n_2,  CnH2n_4, 
CnH2n_.6,  CnH2n_8,  etc.,  as  far  as  CnH2n_.32,  or  C^H^.    Each 
of  these  has  a  large  number   of  representatives,  as  was 
found  in  the  marsh-gas  series.    Not  far  from  two  hundred 
direct  compounds  of  C  and  H  are  known,  not  to  mention 
substitutions.      The   formula  CnH2n_6  represents  a  large 
and  interesting  group  of  compounds,  called  the  benzine 
series.     This  is  the  basis  of  the  aniline  dyes,  and  of  many 
perfumes  and  flavors. 


CHAPTER   LV. 

ILLUMINATING    GAS. 

304.  Source.  —  The  three  main   elements  in  combus- 
tion are  O,  H,  C.     Air  supplies  O,  the  supporter ;    C  and 
H  are  usually  united,  as  hydro-carbons,  in  luminants  and 
combustibles.      H  gives  little  light  in  burning;  C  gives 
much.     The  fibers  of  plants   contain   hydro-carbons,  and 
by  destructive   distillation  these  are  separated,  as  gases, 
from  wood  and  coal,  and  used  for  illuminating  purposes. 
Mineral  coal  is  fossilized  vegetable  matter ;  anthracite  has 
had  most  of  the  volatile  hydro-carbons  removed  by  dis- 
tillation in  the  earth;  bituminous  and  cannel  coals  retain 
them.     These  latter  coals  are  distilled,  and  furnish  us  illu- 
minating gas. 

Experiment  129.  —  Put  into  a  t.t.  20&  of  cannel  coal  in  fine  pieces. 
Heat,  and  collect  the  gas  over  H2O.  Test  its  combustibility.  Notice 
any  impurities,  such  as  tar,  adhering  to  the  sides  of  the  t.t.,  or  of  the 
receiver  after  combustion.  Try  to  ignite  a  piece  of  cannel  coal  by 
holding  it  in  a  Bunsen  flame.  Is  it  the  C  which  burns,  or  the  hydro- 
carbons? Distil  some  wood  shavings  in  a  small  ignition -tube,  and 
light  the  escaping  gas. 

305.  ^Preparation  and  Purification.  —  To   make  illu- 
minating gas,  fire-clay  retorts  filled  with  coal  are  heated 
to  1100°  or  more,  over  a  fire  of  coke  or  coal.      Tubes  lead 
the  distilled    gas  into   a   horizontal   pipe,  called  the  hy- 
draulic main,  partly  filled  with  water,  into  which  the  ends 
of  the  gas-pipe  dip.,    The  gas  then   passes  through  con- 
densers consisting  of  several  hundred  feet  of  vertical  pipe, 
through  high  towers,  called  washers,  in  which  a  fine  spray 


ILLUMINATING  GAS. 


181 


182  ILLUMINATING   GAS. 

of  water  falls,  into  chambers  with  shelves  containing  the 
purifiers  CaO  or  hydrated  Fe2O3,  and  finally  into  a  gas- 
holder, whence  it  is  distributed.  At  the  hydraulic  main, 
condensers,  washers,  and  purifiers,  certain  impurities  are 
removed  from  the  gas.  Coke  is  the  solid  C  residue  after 
distillation.  Gas-carbon,  also  a  solid,  is  formed  by  the 
separation  of  the  heavier  hydro-carbons  at  high  tempera- 
ture, and  is  deposited  on  the  sides  of  the  retort. 

Coal  gas,  as  it  leaves  the  retort,  has  many  impurities.  It  is  accompa- 
nied with  about  %  its  weight  of  coal  tar,  |  its  weight  of  H20  vapor,  -^ 

NH3,  2*5  C02>  -fa  to  -so  H2S>  sis  to  vfa  S  in  other  forras-  The  tar  is  mostly 
taken  out  at  the  hydraulic  main,  which  also  withdraws  some  H20  with  other 
impurities  in  solution.  The  condensers  remove  the  rest  of  the  tar,  and  the 
H2O,  except  what  is  necessary  to  saturate  the  gas.  At  the  main,  the  con- 
densers, and  the  washers,  NH3  is  abstracted,  C02  and  H2S  are  much  re- 
duced, and  the  other  S  compounds  are  diminished.  Lime  purification 
removes  C02  and  H2S,  and,  to  some  extent,  other  S  compounds.  Iron 
purification  removes  H2S.  Fe203  +  3  H2S  =  2  FeS  +  S  +  3  H20. 

The  FeS  is  revivified  by  exposure  to  the  air.  2  FeS  +  O3  =  Fe203  +  2  S. 
It  can  then  be  used  again.  H2S,  if  not  separated,  burns  with  the  gas, 
forming  H2S03,  which  oxidizes  in  the  air  to  H2S04 ;  hence  the  need  of  re- 
moving it.  CO2  diminishes  the  illuminating  power. 

3O6.  Composition.  —  Even  when  freed  from  its  im- 
purities coal-gas  is  a  very  complex  mixture,  the  chief  com- 
ponents being  nearly  as  follows  :  — 

percent  Diluents,  having  little   C,  give 

H         45.    ")  very  little  light.     Notice  the  small 

CTT        41       I  diluents.  £  -,        .  ,.    ,  , 

vxi4      *j..     r  percentage  01  lummants,  or  liglit- 

c  H        j*3  ^  giving   compounds,  also    the   pro- 

C  H        1.2   V  luminants.  portion  of  C  to  H  in  them. 

C2H4       2.5  .)  Cannel   coal    contains    more   of 

C°2        2'     |  impurities.  the     hellvy    hydro-carbons,   CnH^, 

N,  etc.    2.     j  etc^  than  the  ordinary  bituminous 

1°°  coal.     Ten   per  cent   of  the  coal 


ILLUMINATING  GAS.  183 

should  be  cannel ;  naphtha  is,  however,  often  employed  to 
subserve  the  same  purpose,  one  ton  of  ordinary  bituminous 
coal  requiring  four  gallons  of  oil. 

In  Boston,  7,000,000  cubic  feet  of  gas  have  been  burned 
in  one  day,  consuming  500  tons  of  coal;  the  average  is 
not  more  than  half  that  quantity.  Of  the  other  products, 
coke  is  employed  for  heating  purposes,  gas  carbon  is  used 
to  some  extent  in  electrical  work,  and  coal-tar  is  the  source 
of  very  many  artificial  products  that  were  formerly  only 
of  natural  origin.  NH3  is  the  main  source  of  ammonium 
salts,  and  S  is  made  into  H2SO4. 

3O7.  Natural  Gas  occurs  near  Pittsburg,  Pa.,  and  in  many  other 
places,  in  immense  quantities.  It  is  not  only  employed  to  light  the  streets 
and  houses,  but  is  used  for  fires  and  in  iron  and  glass  manufactories.  It 
is  estimated  that  600,000,000  cubic, feet  are  burned,  saving  10,000  tons  of 
coal  daily  in  Pittsburg.  Only  half  a  dozen  factories  now  use  coal.  More 
than  half  the  gas  is  wasted  through  safety  valves,  on  account  of  the  great 
pressure  on  the  pipes  as  it  issues  from  the  earth. 

These  reservoirs  of  natural  ga?  very  frequently  occur  in  sandstone, 
usually  in  the  vicinity  of  coal-beds,  but  sometimes  remote  from  them.  In 
all  cases  the  origin  of  the  gas  is  thought  to  be  in  the  destructive  distil- 
lation, extending  through  long  geological  periods,  of  coal  or  of  other  vege- 
table or  animal  matter  in  the  earth's  interior. 

Natural  gas  varies  in  composition,  and  even  in  the  same  well,  from 
day  to  day ;  it  consists  chiefly  of  CH^  with  some  other  hydro-carbons. 


CHAPTER   LVI. 

ALCOHOL. 

308.  Fermented  Liquor. 

Experiment  130.  —  Introduce  20CC  of  molasses  into  a  flask  of  200CC, 
fill  it  with  water  to  the  neck,  and  put  in  half  a  cake  of  yeast.  Fit  to 
this  a  d.t.,  and  pass  the  end  of  it  into  a  t.t.  holding  a  clear  solution  of 
lime  water.  Leave  in  a  warm  place  for  two  or  three  days.  Then  look 
for  a  turbidity  in  the  lime  water,  and  account  for  it  (page  79).  See 
whether  the  liquid  in  the  flask  is  sweet.  The  sugar  should  be  changed 
to  alcohol  and  CO2.  This  is  fermented  liquor;  it  contains  a  small 
percentage  of  alcohol. 

309.  Distilled  Liquor. 

Experiment  131.  —  Attach  the  flask  used  in  the  last  experiment 
to  the  apparatus  for  distilling  water  (Eig.  32),  and  distil  not  more 
than^one-fifth  of  the  liquid,  leaving  the  rest  in  the  flask.  The  greater 
part  of  the  alcohol  will  pass  over.  To  obtain  it  all,  at  least  half  of  the 
liquid  must  be  distilled ;  what  passes  over  towards  the  last  is  mostly 
wrater.  Taste  and  smell  the  distillate.  Put  some  into  an  e.d.  and 
touch  a  lighted  match  to  it.  If  it  does  not  burn,  redistil  half  of  the 
distillate  and  try  to  ignite  the  product.  Try  the  combustibility  of 
commercial  alcohol;  of  Jamaica  ginger,  or  of  any  other  liquid  known 
to  contain  alcohol. 

310.  Effect  on  the  System. 

Experiment  132.  —  Put  a  little  of  the  white  of  egg  into  an  e.d. 
or  a  beaker ;  cover  it  with  strong  alcohol  and  note  the  effect.  Strong 
alcohol  has  the  same  coagulating  action  on  the  brain  and  on  the  tis- 
sues generally,  when  taken  into  the  system,  absorbing  water  from  them, 
hardening  them,  and  contracting  them  in  bulk. 


ALCOHOL.  185 

311.  Affinity  for  Water. 

Experiment  133.  —  To  show  the  contraction  in  mixing  alcohol  and 
water,  measure  exactly  5CC  of  alcohol  and  5CC  of  water.  Pour  them  to- 
gether, and  presently  measure  the  mixture.  The  volume  is  diminished. 
A  strip  of  parchment  soaked  in  water  till  it  is  limp,  then  dipped  into 
strong  alcohol,  becomes  again  stiff,  owing  to  the  attraction  of  alcohol 
for  water. 

312.  Purity.  —  The  most  important  alcohols  are  methyl 
alcohol  and   ethyl  alcohol.     The  former,  wood   spirit,  is 
obtained  in  an  impure  state  by  distilling  wood;  it  is  used 
to  dissolve  resins,  fats,  oils,  etc.,  and  to  make  aniline. 
It  is  poisonous,  as  are  the  others. 

Ethyl  alcohol,  spirit  of  wine,  is  the  commercial  article. 
It  is  prepared  by  fermenting  glucose,  and  distilling 
the  product.  It  boils  at  78°,  vaporizing  22°  lower  than 
water,  from  which  it  can  be  separated  by  fractional  dis- 
tillation. By  successive  distillations  of  alcohol  ninety- 
four  per  cent  can  be  obtained,  which  is  the  best  com- 
mercial article,  though  most  grades  fall  far  below  this. 
Five  per  cent  more  can  be  removed  by  distilling  with 
CaO,  which  has  a  strong  affinity  for  water.  The  last  one 
per  cent  is  removed  by  BaO.  One  hundred  per  cent 
constitutes  absolute  alcohol,  which  is  a  deadly  poison. 
Diluted,  it  increases  the  circulation,  stimulates  the  system, 
hardens  the  tissues  by  withdrawing  water,  and  is  the 
intoxicating  principle  in  all  liquors.  It  is  very  inflam- 
mable, giving  little  light,  and  much  heat,  and  readily 
evaporates. 

Beer  has  usually  three  to  six  per  cent  of  alcohol;  wines,  eight  to 
twenty  per  cent.  The  courts  now  regard  all  liquors  having  three  per  cent, 
or  less,  of  alcohol,  as  not  intoxicating.  In  Massachusetts  it  is  one  pet 
cent. 


CHAPTER    LVII. 

OILS,  FATS,  AND  SOAPS. 

313.  Sources  and  Kinds  of  Oils  and  Fats.  —  Oils  and 
fats  are  insoluble  in  water ;  the  former  are  liquid,  the  lat- 
ter solid.  Most  fats  are  obtained  from  animals,  oils  from 
both  plants  and  animals.  Oils  are  classified  as  fixed  and 
essential.  Castor  oil  is  an  example  of  the  former  and  oil 
of  cloves  of  the  latter.  Fixed  oils  include  drying  and  non- 
drying  oils.  They  leave  a  stain  on  paper,  while  essen- 
tial, or  volatile  oils,  leave  no  trace,  but  evaporate  readily. 
Essential  oils  dissolved  in  alcohol  furnish  essences.  They 
are  obtained  by  distilling  with  water  the  leaves,  petals, 
etc.,  of  plants.  Drying  oils,  as  linseed,  absorb  O  from  the 
air,  and  thus  solidify.  Non-drying  ones,  as  olive,  do  not 
solidify,  but  develop  acids  and  become  rancid  after  some 
time. 

Oils  and  fats  are  salts  of  fatty  acids  and  the  base  gly- 
cerin. The  three  most  common  of  these  salts  are  ole'in, 
found  in  olive  oil,  palmitin,  in  palm  oil  and  human  fat, 
and  stearin,  in  lard.  The  first  is  liquid,  the  second  semi- 
solid,  the  last  solid.  Most  fats  are  mixtures  of  these  and 
other  salts. 


Glyceryl 


Olei'n       = 


Palmitin  =  v.  salts  from 


oleate 

glyceryl 


Stearin     = 


palmitate  j 
Glyceryl 
stearate     J 


oleic 


palmitic 


stearic 


acid,    and 


hydrate. 


OILS,   FATS,   AND    SOAPS.  187 

314.  Saponification   consists  in  separating  these  salts 
into  their  acids   and   the   base  glycerin  ;   soap-making  is 
the  best  illustration.     To  effect  this  separation,  a  strong 
soluble  base  is  used,  KOH  for  soft,  and  NaOH  for  hard 
soap.     Study  this  reaction  : 

Glyceryl  oleate        1      ,dium  |  f  oleate        |       |giyceryl 

Glycery   palmitate     +  U  sodium      palmitate     + 

Glyceryl  stearate     )      (    y  [  stearate    J       [    J 

Soaps  are  thus  salts  of  fatty  acids  and  of  K  or  Na. 

315.  Soap   is   soluble  in  soft   water,   but   the    sodium 
stearate    probably   unites  with    water  to  form    hydrogen 
sodium  stearate  and  NaOH.     The  grease   which  exudes 
from   the    skin,  or  appears  in  fabrics  to   be    washed,  is 
attacked  by  this  NaOH  and  removed,  together  with  the 
suspended  dirt,  and  a  new  soap  is  formed  and  dissolved 
in  the  water.     Hard  water  contains  salts  of  Ca  and  Mg, 
and  when  soap  is  used  with  it  the  Na  is  at  once  replaced 
by  these  metals,  and  insoluble  Ca  or  Mg  soaps  are  formed. 
Hence  in  hard  water  soap  will  not  cleanse  till  all  the  Ca 
and  Mg  compounds  have  combined. 

316.  Glycerin,  C3H5(OH)3,  is  a  sweet,  thick,  colorless, 
unctuous  liquid,  used  in  cosmetics,   unguents,   pomades, 
etc.     It  is  prepared  in  quantity  by  passing  superheated 
steam  over  fats  when  under  pressure. 

317.  Dynamite.  —  Treated  with  HNO3  and  H2SO4  glycerin  forms 
the  very  explosive  and  poisonous  liquid  nitro-glycerin.    In  this  process  the 
C3H5(OH)3  becomes  C3H5(NO3)3.     C3H5(OH)3  +  3  HN03  =  C3H5(NO3)3  + 
3  H2O.    H2S04  is  used  to  absorb  the  H2O  which  is  formed.    Nitro-glycerin, 
absorbed  by  gunpowder,  diatomaceous  earth,  sawdust,  etc.,  forms  dynamite. 
For  obvious  reasons  the  pupil  should  not  experiment  with  these  substances. 

318.  Butter  and  Oleomargarine. —Milk  contains  minute 
particles  of  fat,  about  ^  of  au  inch  in  diameter,  which  give  it  the  white 


188  OILS,   FATS,   AND   SOAPS. 

color.  These  particles  are  lighter  than  the  containing  liquid,  and  rise  to 
the  top  as  cream.  Churning  unites  the  particles  more  closely,  and  sep- 
arates them  from  the  buttermilk.  The  flavor  of  butter  is  due  to  the 
presence  of  five  or  ten  per  cent  of  butyric  and  other  acids  of  the  same 
series. 

It  was  found  that  cows  gave  milk  after  they  ceased  to  have  food ;  hence 
it  was  inferred  that  the  milk  was  produced  at  the  expense  of  the  cows'  fat. 
Why  could  not  butter  be  artificially  made  from  the  same  fat  ?  It  was  but  a 
step  from  fat  to  milk,  as  it  was  from  milk  to  butter.  Oleomargarine,  or 
butterine,  was  the  result.  Beef  fat,  suet,  is  washed  in  water,  ground  to 
a  pulp,  and  partially  melted  and  strained,  the  stearin  is  separated  from 
the  filtered  liquid  and  made  into  soap,  and  an  oily  liquid  is  left.  This  is 
salted,  colored  with  annotto,  mixed  with  a  certain  portion  of  milk,  and 
churned.  The  product  is  scarcely  distinguishable  from  butter,  and  is 
chemically  nearly  identical  with  it,  though  less  likely  to  become  rancid 
from  the  absence  of  certain  fatty  acids ;  its  cost  is  perhaps  one-third  as 
much  as  chat  of  but,r*-r. 


CHAPTER   LVIII. 

CA  RB  O-H  YDR  A  TE  S. 

319.  Carbon  and  Water.  —  Some  very  important  or- 
ganic compounds  have  H  and  O,  in  the  proper  proportion 
to  form  water,  united  with  C      The  three  leading  ones  are 
sugar,  C^H^On  or    Cj2(H2O)n,  starch,  C6H10O5  or  ?,  and 
cellulose,    C18H3oO15   or  ?.      Note   the   significance   of  the 
name  carbo-hydrates  as  applied  to  them. 

320.  Sugars  may  be  divided  into  two  classes,  —  the 
sucroses,  Ci2H22On,  and  the   glucoses,  C6H12O6.     Sucrose, 
the  principal  member  of  the  first  class,  is  obtained  from 
the  juice  of  the  maple,  the  palm,  the  beet  and  the  sugar- 
cane ;  in  Europe  largely  from  the  beet,  in  America  from 
cane.     Granulated  sugar  is  that  which  has  been  refined ; 
brown  sugar  is  the  unrefined.     From  the  sap  evaporated 
by  boiling,   brown    sugar    crystallizes,  leaving   molasses, 
which   contains    glucose    and    other   substances.      Good 
molasses   has   but   a    small    percentage   of  glucose.     To 
refine    brown    sugar   it   is    dissolved   in   water,   a   small 
quantity  of  blood  is  added  to  remove  certain  vegetable  sub- 
stances, after  which  it  is  filtered  through  animal  charcoal, 
i.e.  bone-black,  a  process  which   takes   out  the  coloring- 
matter.     The  water  is  then    evaporated  in  vacuum-pans, 
so  as  to  boil  at  about  74°  and  to  prevent  conversion  into 
grape  sugar.     By  this  process  much  glucose  or  syrup  is 
formed,  which  is  separated  from  the  crystalline  sucrose  by 
rapidly  revolving  centrifugal  machines. 


190  CARBOHYDRATES. 

Great  quantities  of  sucrose  are  used  for  food  by  all  civil- 
ized nations.  A  single  refinery  in  New  York  purifies 
2,000,000  pounds  per  day. 

321.  Glucose,  or  invert  sugar,  the  principal  member  of 
the  second  class,  consists  of  two  distinct  kinds  of  sugar, 
—  dextrose  and  levulose.     These  differ  in  certain  proper- 
ties, but  have  the  same  symbol.    Both  are  found  in  equal 
parts  in  ripe  fruits,  while    sucrose  occurs  in  the  unripe. 
Honey  contains  these  three  kinds  of  sugar. 

Sucrose,  by  the  action  of  heat,  weak  acids,  or  ferments, 
may  be  resolved  into  the  other  two  varieties.  C^H^Ou  + 
H2O  =  C6H12O6+C6H12O6.  No  mode  of  reversing  this  pro- 
cess, or  of  transforming  glucose  into  sucrose  is  known. 
Glucose  is  easily  made  from  starch  or  from  the  cellulose 
in  cotton  rags,  sawdust,  etc.  If  boiled  with  dilute  H2SO4 
starch  takes  up  water  and  becomes  glucose.  C6H10O6-f 

H20  =  C6HW06. 

CaCO3  is  added  to  precipitate  the  H2SO4,  which  remains 
unchanged.  State  the  reaction.  The  product  is  filtered 
and  the  filtrate  is  evaporated.  Much  glucose  is  made 
from  the  starch  of  corn  and  potatoes. 

322.  Starch  is  found  in  all  plants,  especially  in  grains, 
seeds,  and  tubers.     Green  plants  —  those  containing  chlo- 
rophyll—  manufacture  their   own   starch   from  CO2  and 
H2O.     These  chlorophyll  grains  are  the  plant's  chemical 
laboratories,  and  hundreds  of  thousands  of  them  exist  in 
every  leaf.     CO2  and  a  very  little  H2O  enter  the  leaf  from 
the  air,  H2O  being  also  drawn  up  through  the  root  and 
stem   from   the   earth.     In   some    unknown  way  in   the 
leaf,  light  has  the  power  of  synthesizing  these  into  starch 
and  setting  free  O,  which  is  returned  to  the  atmosphere. 


CARBO-HYDRATES.  191 

6  CO2  4-  5  H2O  =  C6H10O5  +  12  O.  As  no  such  change  takes 
place  in  darkness,  all  green  plants  must  have  light.  Par- 
asitic plants,  which  are  usually  colorless,  obtain  starch 
ready-made  from  those  on  which  they  feed. 

323.  Uses.  —  Glucose  is  used  in  the  manufacture   of 
alcohol  and  cheap  confectionery,  and  in  adulterating  su- 
crose.    It  is  only  two-thirds  as  sweet  as  the  latter.     The 
seeds  of  all   plants    contain   starch   for   the   germinating 
sprout  to  feed  upon ;  but  starch  is  insoluble,  and  hence 
useless  until  it  is  converted  into  glucose.     This  is  effected 
by  the  action  of  warmth,  moisture,  and  a  ferment  in  the 
seed.     Glucose  is  soluble  and  is  at  first  the  plant's  main 
food. 

Commercial  starch  is  made  in  the  United  States  chiefly 
from  corn ;  in  Europe,  from  potatoes.  Differences  in  the 
size  of  starch  granules  enable  microscopists  to  determine 
the  plant  to  which  they  belong. 

324.  Cellulose,  or  woody  fiber,  is  the  basis  of  all  vege- 
table cell  walls.     Cotton  fiber  represents  almost  pure  cel- 
lulose.    From  it  are  made  paper  and  woven  tissues.     In 
paper   manufacture,  woody  fiber    is    made    into  a   pulp, 
washed,   bleached,   filtered,    hot-pressed,    and    sometimes 
glazed.     Parchment  paper,  vegetable  parchment,  is  made 
by  dipping  unglazed   paper  for  half  a   minute  into  cold 
dilute  H2SO4,  1  part  H2O,  2J  parts  H2SO4,  and  then  wash- 
ing.    The  fiber,  by  chemical  change,  is  thus  toughened. 
The  cell  walls  of  wood  are  impure  cellulose ;  hence  the 
inferior  quality  of  paper  made  from  wood-pulp.     Paper  is 
now  employed  for  a  large  number  of  purposes  for  which 
wood  has  heretofore  been  used,  such  as  for  barrels,  pails, 
and  other  hollow  ware,  wheels,  etc. 


192  CARBO-HYDRATES. 

325.  Gun-cotton   is  made  by  treating  cotton  fiber  with  H2SO4 
and  HNO3,  washing  and  drying.     To  all  appearances  no  change  has  taken 
place,  but  the  substance  has  become  an  explosive  compound. 

326.  Dextrin,  a  gufnmy  substance  used  for  the  backs  of  post- 
age  stamps,  is  a  carbo-hydrate,  as  in  fact  are  gums  in  general.      Dex- 
trin is  made  by  heating  starch  with  H2SO4  at  a  lower  temperature  than 
for  dextrose. 

32  7.  Zylonite  and  Celluloid.  —  These  two  similar  substances 
embody  the  latest  use  of  cellulose  in  manufactured  articles.  For  zylonite, 
linen  paper  is  cut  into  strips  two  feet  by  one  inch,  soaked  ten  minutes  in  a 
mixture  of  H2S04  and  HN03,  a  process  called  nitration,  washed  for  sev- 
eral hours,  then  ground  to  a  fine  pulp,  and  thoroughly  dried.  It  is  then 
similar  to  pyroxiline.  Aniline  coloring-matter  of  any  desired  shade  is 
added,  after  which  it  is  dissolved  by  soaking  some  hours  in  alcohol  and 
camphor,  the  liquid  is  evaporated,  and  the  substance  is  kneaded  between 
steam-heated  iron  rollers,  dried  with  hot  air,  and  finally  subjected  to  great 
pressure,  to  harden  it,  and  cut  into  sheets.  Zylonite  is  combustible  at  a 
low  temperature,  and  when  in  the  pyroxiline  stage,  explosively  so.  Ivory, 
coral,  amber,  bone,  tortoise  shell,  malachite,  etc.,  are  so  closely  imitated 
that  the  imitation  can  only  be  detected  by  analysis.  Collars,  combs, 
canes,  piano-keys,  and  jewelry,  are  manufactured  from  it,  and  it  can  be 
made  transparent  enough  for  windows. 


CHAPTER  LIX. 
CHEMISTRY  OF  FERMENTATION. 

328.  Ferments.  —  A  large  number  of  chemical  changes 
are  brought  about  through  the  direct  agency  of  bodies 
called  ferments  ;  their  action  is  called  fermentation.     Fer- 
ments are  sometimes  lifeless  chemical  products  found  in 
living  bodies;  but  in  other  cases  they  are  humble  plants. 

329.  Yeast  is  one  of  the  most  common  of  living  fer- 
ments, wild  yeast  being  a  microscopic  plant  found  on  the 
ground  near  apple-trees  and  grape-vines,  and  often  in  the 
air.     The  cultivated  variety  is  sold  by  grocers.     The  tem- 
perature best  suited  to  the  rapid  multiplication  of  the 
germs  forming  the  ferment  plant  is  25°  to  35°. 

330.  Alcoholic     and    Acetic     Fermentation.  —  The 

changes  which  the  juice  of  the  apple  undergoes  in  form- 
ing cider  and  vinegar  are  a  good  illustration  of  fermen- 
tation by  a  living  plant.  Apple-juice  contains  sucrose. 
Yeast  germs  from  the  air,  getting  into  this  unfermented 
liquor,  cause  it  to  "  work."  This  process  changes  sucrose 
to  glucose,  and  glucose  to  alcohol  and  CO2,  and  is  known 
as  alcoholic  fermentation.  The  latter  reaction,  C6H12O6= 
2  C2H6O  +  2  CO2,  is  only  partially  correct,  as  other  prod- 
ucts are  formed.  The  juice  has  now  become  cider;  the 
sugar,  alcohol.  After  a  time,  if  left  exposed,  another  or- 
ganism finds  its  way  to  the  alcohol,  and  transforms  it  into 
acetic  acid,  HC2H3O2,  and  H2O.  This  process  is  called 


194  CHEMISTRY   OF   FERMENTATION. 

acetic  fermentation.  C2H6O  +  O2  =  HC2H3O2  +  H2O.  For 
this  fermentation,  a  liquor  should  not  have  over  ten  per 
cent  of  alcohol.  Mother  of  vinegar  consists  of  the  germs 
that  caused  the  fermentation.  Still  a  third  species  of  fer- 
ment may  cause  another  action,  changing  acetic  acid  to 
H2O  and  CO2.  The  vinegar  then  tastes  flat.  HC2H3O2  + 


Some  mineral  acids,  as  H2SO4  and  HC1,  and  some  organic 
acids,  are  regarded  as  lifeless  ferments.  To  this  class  are 
thought  to  belong  the  diastase  of  malt  and  the  pepsin  of 
the  stomach.  This  variety  of  ferments  exists  in  the  seeds 
of  all  plants,  and  changes  starch  to  glucose. 

331.  Bread  which  is  raised  by  yeast  is  fermented,  the  object  being 
to  produce  C02,  bubbles  of  which,  with  the  alcohol,  cause  the  dough  to 
rise  and  make  the  bread  light. 

Grapes  and  other  fruits  ferment  and  produce  wines,  etc.,  from  which 
distilled  liquors  are  obtained. 

332.  Lactic  Fermentation  changes  the  sugar  of  milk,  lactose, 
to  lactic  acid,  i.e.  sour  milk.     In  canning  fruit,  any  germs  present  are 
killed  by  heating,  and  those  from  the  air  are  excluded  by  sealing  the  can. 
Milk  has  been  kept  sweet  for  years  by  boiling,  and  tightly  covering  the 
receptacle  with  two  or  three  folds  of  cotton  cloth. 

333.  Putrefaction  is  fermentation  in  which  the  prod- 
ucts of   decay  are  ill-smelling.      Saprophytes  attack  the 
dead  matter,  feed  on  it,  and  cause  it  to  putrefy.     This 
action,  as  well  as  that  of  ordinary  fermentation,  used  to  be 
attributed  solely  to  oxygen.      Germs  bring  back  organic 
matter  to  a  more  elementary  state,  and  so  have  a  very  im- 
portant function.    By  some  scientists,  digestion  is  regarded 
as  a  species  of  fermentation,  probably  due  to  the  action  of 
lifeless  ferments  ;  e.g.  sucrose  cannot  be  taken  into  the  sys- 
tem, but  is  first  fermented  to  glucose. 


CHEMISTRY    OF   FERMENTATION.  195 

334.  Most  Infectious  Diseases  are  now  thought  to  be 
due  to  parasites  of  various  kinds,  such  as  bacteria,  mi- 
crobes, etc.,  with  which  the  victim  often  swarms,  and  which 
feed  on  his  tissues,  multiplying  with  enormous  rapidity. 
Such  diseases  are  small-pox,  intermittent  and  yellow  fevers, 
etc.  Consumption,  or  tuberculosis,  is  believed  to  be  caused 
by  a  microbe  which  destroys  the  lungs.  In  some  diseases 
not  less  than  fifteen  billions  of  the  organisms  are  estimated 
to  exist  in  a  cubic  inch.  These  multiply  so  rapidly  that 
from  a  single  germ  in  fortj^-eight  hours  may  be  produced 
nearly  three  hundred  billions.  These  germs  do  not  spring 
into  life  spontaneously  from  inorganic  matter,  but  come 
from  pre-existent  similar  forms.  Parasites  are  not  so  rare 
in  the  system  even  of  a  healthy  person  as  is  generally 
supposed.  They  are  found  on  our  teeth  and  in  many  of 
the  tissues  of  the  body. 

Several  infectious  diseases  are  now  warded  off  or  ren- 
dered less  virulent  by  vaccination,  the  philosophy  of  which 
is  that  the  organisms  are  rendered  less  dangerous  by 
domestication ;  several  crops,  or  generations,  are  grown 
in  a  prepared  liquid,  each  less  injurious  than  its  parent. 
Some  of  the  more  domesticated  ones  are  introduced  into 
the  system,  and  the  person  has  only  a  modified  form  of  the 
disease,  often  scarcely  any  at  all,  and  is  for  a  more  or  less 
limited  time  insured  against  further  danger. 

Dust  particles  and  motes  floating  in  the  air  are  in  part 
germs,  living  or  dead,  often  requiring  only  moisture  and 
mild  temperature  for  resuscitation.  Most  of  these  are 
harmless. 


CHAPTER   LX. 
CHEMISTRY  OF  LIFE. 

335.  Growth.  —  The  chemistry  of  organic  life  is  very 
complex,  and  not  well  understood.     A  few  of  the  principal 
points  of  distinction  between  the  two  great  classes  of  living 
organisms,  plants  and  animals,  are  all  that  can  be  noted  here. 
Minerals  grow  by  accretion,  i.e.  by  the  external  addition 
of  molecules  of  the   same  material  as  their  interior.     A 
crystal  of  quartz  grows  by  the  addition  of  successive  mole- 
cules of  SiO2,  arranged  in  a  symmetrical  manner  around 
its  axis.    The  growth  of  crystals  can  be  seen  by  suspending 
a  string  in  a  saturated  solution  of  CuSO4,  or  of  sugar.     In 
plants  and  animals  the  growth  is  very  much  more  complex, 
but  is  from  the  interior,  and  is  produced  by  the  multipli- 
cation of  cells.     To  produce  this  cell-growth  and  multipli- 
cation, food-materials  must  be  furnished  and  assimilated. 
In  plants,   sap  serves   to   carry  the  food-materials  to  the 
parts  where  they  are  needed.     In  the  higher  animals,  vari- 
ous fluids,  the  most  important  of  which  is  the  blood,  serve 
the  same  purpose. 

336.  Chemistry   of    Plants.  —  In    ultimate    analysis, 
plants  consist  mainly  of  C,  H,  O,  N,  P,  K.     In  proximate 
analysis,  as  it  is  called,  they  are  found  to  contain  these 
elements  combined  to  form  substances  like  starch,  sugar, 
etc.     Water  is  the  leading  compound  in  both  animals  and 
plants.    One  of  the  most  important  differences  between  ani- 
mals and  plants  is,  that  all  plants,  except  parasitic  ones, 
are  capable  of  building  up  such  compounds  as  starch  from 


CHEMISTRY   OF   LIFE.  197 

mineral  food-stuffs,  while  animals  have  not  that  power,  but 
must  have  the  products  of  proximate  analysis  ready  pre- 
pared, as  it  were,  by  the  plant.  Hence  plants  thrive  on 
minerals,  whereas  animals  feed  on  plants  or  on  other  ani- 
mals. The  power  which  plants  have  of  transforming 
mineral  matter  is  largely  due  to  sunlight,  the  action  of 
which  in  separating  CO2  was  described  on  page  82.  The 
reaction  in  the  synthesis  of  starch  from  CO2  and  H2O  in 
the  leaf,  is  thought  to  be  as  follows :  6  CO2  +  5  H2O  = 
C6H10O5  + 12  O.  C6H10O5  is  taken  into  the  tree  as  starch ; 
12  O  is  given  back  to  the  air.  All  the  constituents,  ex- 
cept CO2  and  a  very  small  quantity  of  H2O,  are  absorbed 
by  the  roots,  from  the  soil,  from  which  they  are  soon 
withdrawn  by  vegetation.  To  renew  the  supply,  fertilizers 
or  manures  are  applied  to  the  soil.  These  must  contain 
compounds  of  N,  P,  and  K.  N  is  usually  applied  in  the 
form  of  ammonium  compounds,  e.g.  (NH4)2SO4,  (NH4)2CO3, 
and  NH4NO3.  The  reduction  and  application  of  Ca3(PO4)2 
for  this  purpose  was  described  on  page  123.  K  is  usually 
applied  in  the  form  of  KC1  and  K2SO4. 

337.  Food  of  Man.  —  In  the  higher  animals  the  object 
is  not  so  much  to  increase  the  size  as  to  tsupply  the  waste 
of  the  system.  The  principal  elements  in  man's  body  are 
C,H,  0,N,  S,P. 

An  illustration  of  the  transformation  of  mineral  foods 
by  plants  before  they  can  be  used  by  animals  is  found  in 
the  Ca3(PO4)2  of  bones.  This  is  rendered  soluble  ;  plants 
absorb  and  transform  it ;  animals  eat  the  plants  and  obtain 
the  phosphates.  Thus  man  is  said  to  "  eat  his  own  bones." 
The  food  of  mankind  may  be  divided  into  four  classes : 
(1)  proteids,  which  contain  C,  H,  O,  N,  and  often  S  and 
P;  (2)  fats,  and  (3)  amyloids,  both  of  which  contain  C, 


198  CHEMISTRY   OF   LIFE. 

H,  O ;  (4)  minerals.  Examples  of  the  first  class  are  the 
gluten  of  flour,  the  albumen  of  the  white  of  egg,  and 
the  casein  of  cheese.  To  the  second  class  belong  fats  and 
oils;  to  the  third,  starch,  sugar,  and  gums;  to  the  fourth, 
H2O,  NaCl  and  other  salts.  Since  only  proteids  contain 
all  the  requisite  elements,  they  are  essential  to  human 
food,  and  are  the  only  absolutely  essential  ones,  except 
minerals ;  but  since  they  do  not  contain  all  the  elements 
in  the  proportion  needed  by  the  system,  a  mixed  diet  is  in- 
dispensable. Milk,  better  than  any  other  single  food,  sup- 
plies the  needs  of  the  system.  The  digestion  and  assimi- 
lation of  these  food-stuffs  and  the  composition  of  the 
various  tissues  is  too  complicated  to  be  taken  up  here;  for 
their  discussion  the  reader  is  referred  to  works  on  physio- 
logical chemistry. 

338.  Conservation.  — •  Plants,  in  growing,  decompose 
CO2,  and  thereby  store  up  energy,  the  energy  derived  from 
the  light  and  heat  of  the  sun.  When  they  decay,  or  are 
burned,  or  are  eaten  by  animals,  exactly  the  same  amount 
of  energy  is  liberated,  or  changed  from  potential  to  kinetic, 
and  the  same  amount  of  CO2  is  restored  to  the  air.  The 
tree  that  took  a  hundred  years  to  complete  its  growth 
may  be  burned  in  an  hour,  or  be  many  years  in  decaying; 
but  in  either  case  it  gives  back  to  its  mother  Nature,  all  the 
matter  and  energy  that  it  originally  borrowed.  The  ash 
from  burning  plants  represents  the  earthy  matter,  or  salts, 
which  the  plant  assimilated  during  its  growth ;  the  rest  is 
volatile.  In  the  growth  and  destruction  of  plants  or  of  ani- 
mals, both  energy  and  matter  have  undergone  transforma- 
tion. Animals,  in  feeding  on  plants,  transform  the  energy  of 
sunlight  into  the  energy  of  vitality.  Thus  "  we  are  chil- 
dren of  the  sun." 


CHAPTER   LXI. 
THEORIES. 

339.  The    La   Place   Theory.  — This  theory  supposes  that  at 
one  time  the  earth  and  the  other  planets,  together  with  the  sun,  constituted 
a  single  mass  of   vapor,   extending   billions  of  miles  in  space ;   that  it 
rotated  around  its   center;   that  it  gradually  shrank  in  volume  by  the 
transformation  of  potential  into  kinetic  energy ;  that  portions  of  its  outer 
rim  were  thrown  off,  and  finally  condensed  into  planets ;  that  our  sun  is 
only  the  remainder  of  that  central  mass  which  still  rotates  and  carries 
the  planets  around  with  it ;  that  the  earth  is  a  cooling  globe ;  that  the 
other  planets  are  going  through  the  same  phases  as  the  earth  ;  and  finally 
that  the  sun  itself  is  destined  like  them  to  become  a  cold  body. 

340.  A  Cooling"  Earth.  —  The  sun's  temperature  is  variously  es- 
timated at  many  thousands,  or  even  millions  of  degrees.    Many  metals  which 
exist  on  the  earth  as  solids  —  e.g.  iron  —  are  gases  in  the  dense  atmosphere 
of  the  sun.      Thus   the   earth,  in   its   early   existence,  must  have  been 
composed  of  gases  only,  which  in  after  ages  condensed  into  liquids  and 
solids. 

So  intense  was  the  heat  at  that  time,  that  substances  probably  existed 
as  elements  instead  of  compounds,  i.e.  the  temperature  was  above  the 
point  of  dissociation.  We  have  seen  that  A12O3,  CaO,  SiO2,  etc.,  are 
dissociated  at  the  highest  temperatures  only.  If  the  temperature  were 
above  that  of  combination,  compounds  could  not  exist  as  such,  but  matter 
would  exist  in  its  elemental  state.  On  slowly  cooling,  these  elements  would 
combine.  It  is,  then,  a  fair  inference  that  such  compounds  as  need  the 
highest  temperatures  to  separate  them,  as  silica,  silicates,  and  some 
oxides,  were  formed  from  their  elements  at  a  much  earlier  stage  of  the 
earth's  history  than  were  those  compounds  that  are  more  easily  separ- 
able, such  as  water,  lead  sulphide,  etc.,  and  that  the  most  infusible  sub- 
stances were  solidified  first. 

341.  Evolution.  —  As  the   earth  slowly  cooled,  elements  united 
to  form  compounds,  gases  condensed  to  liquids,  and  these  to  solids.     At 
one  time  the  entire  surface  of  our  planet  may  have  been  liquid.     When 
the  cooling  surface  reached  a  point   somewhat  below  that  of  boiling 


200  THEORIES. 

water,  the  lowest  forms  of  life  appeared  in  the  ocean.  This  was  many  mil- 
lions of  years  ago.  Most  scientists  believe  that  all  vegetable  and  animal 
life  has  developed  from  the  lowest  forms  of  life.  There  is  also  a  theory 
that  all  chemical  elements  are  derivatives  of  hydrogen,  or  of  some  other 
element,  and  that  all  the  so-called  elements  are  really  compounds,  which 
a  sufficiently  high  temperature  would  dissociate.  As  evidence  of  this,  it 
is  said  that  less  than  half  as  many  elements  have  been  discovered  in  the 
sun  as  in  the  earth,  and  that  comets  and  nebulae,  which  are  less  devel- 
oped forms  of  matter  than  the  sun,  have  a  few  simple  substances  only. 

It  is  oasy  to  fancy  that  all  living  bodies,  both  animal  and  vegetable,  are 
only  natural  growths  from  the  lowest  forms  of  life;  that  these  lowest 
forms,  are  a  development,  with  new  manifestations  of  energy,  from  inor- 
ganic matter;  that  compounds  are  derived  from  elements;  and  that  the 
last  are  derivatives  of  some  one  element ;  but  it  must  be  borne  in  mind 
that  this  is  only  a  theory. 

342.  New  Theory  of  Chemistry.  —  We  have  seen  that  heat 
lies  at  the  basis  of  chemical  as  well  as  of  physical  changes.  By  the  loss 
of  heat,  or  perhaps  by  the  change  of  potential  into  kinetic  energy,  in  a 
nebulous  parent  mass,  planets  were  formed,  capable  of  supporting  living 
organisms.  Heat  changes  solids  to  liquids,  and  liquids  to  gases ;  it  re- 
solves compounds,  or  it  aids  chemical  union.  In  every  chemical  combina- 
tion heat  is  developed ;  in  every  case  of  dissociation  heat  is  absorbed. 
Properly  written,  every  equation  should  be :  a  +  b  =  c  -f  heat ;  e.g.  2  H  +  O 
=  H2O  +  heat ;  or,  c  —  a  =  b  —  heat ;  e.g.  H20  —  2  H  =  0  —  heat.  Another 
illustration  is  the  combination  of  C  and  0,  and  the  dissociation  of  C02,  as 
given  on  page  82.  C  +  O2  =  C02  +  energy.  CO2  —  02  =  C  -  energy.  In 
fact,  there  are  indications  that  the  present  theory  of  atoms  and  molecules  of 
matter,  as  the  foundation  of  chemistry,  will  at  no  distant  day  give  place 
to  a  theory  of  chemistry  based  on  the  forms,  of  energy,  of  which  heat  is  a 
manifestation. 


CHAPTER   LXII. 

VOLUMES   AND    WEIGHTS. 

343.    Oxygen. 

Experiment  134.  —  Weigh  accurately,  using  delicate  balances, 
5e  KC1O3,  and  mix  with  the  crystals  1  or  2*  of  pure  powdered  MnO2. 
Put  the  mixture  into  a  t.t.  with  a  tight-fitting  cork  and  delivery-tube, 
and  invert  over  the  water-pan,  to  collect  the  gas,  a  flask  of  at  least 
one  and  a  half  liters'  capacity,  filled  with  water.  Apply  heat,  and, 
without  rejecting  any  of  the  gas,  collect  it  as  long  as  any  will  separate. 
Then  press  the  flask  down  into  the  water  till  the  level  in  the  flask  is 
the  same  as  that  outside,  and  remove  the  flask,  leaving  in  the  bottom 
all  the  water  that  is  not  displaced.  Weigh  the  flask  with  the  water  it 
contains ;  then  completely  fill  it  with  water  and  weigh  again.  Sub- 
stract  the  first  weight  from  the  second,  and  the  result  will  evidently 
be  the  weight  of  water  that  occupies  the  same  volume  as  the  O  col- 
lected. This  weight,  if  expressed  in  grams,  represents  approximately 
th«  number  of  cubic  centimeters  of  water,  —  since  lcc  of  water  weighs 
1&,  —  or  the  number  of  cubic  centimeters  of  O. 

At  the  time  the  experiment  is  performed  the  temperature  should 
be  noted  with  a  centigrade  thermometer,  and  the  atmospheric  pres- 
sure with  a  barometer  graduated  to  millimeters. 

Suppose  that  we  have  obtained  1450CC  of  O,  that  the  temperature  is 
27°,  and  the  pressure  758mm;  we  wish  to  find  the  volume  and  the 
weight  of  the  gas  at  0°  and  760mm. 

According  to  the  law  of  Charles  —  Physics,  page  132  —  the  volume 
of  a  given  quantity  of  gas  at  constant  pressure  varies  directly  as  the 
absolute  temperature.  To  reduce  from  the  centigrade  to  the  absolute 
scale,  we  have  only  to  add  273°.  Adding  the  observed  temperature, 
we  have  273°  +  27°  =  300°.  Applying  the  above  law  to  O  obtained 
at  300°  A,  we  have  the  proportion  below.  Since  the  volume  of  O  at 
273°  will  be  less  than  it  will  at  300°,  the  fourth  term,  or  answer 
will  be  less  than  the  third,  and  the  second  term  must  be  less  than 


202  GAS   VOLUMES    AND    WEIGHTS. 

the  first.  300  :  273  :  :  1450  :  x.  This  would  give  the  result  dependent 
upon  temperature  alone. 

By  the  law  of  Mariotte  —  Physics,  page  40  —  the  volume  of  a 
given  quantity  of  gas  at  a  constant  temperature  varies  inversely  as 
the  pressure.  Applying  this  law  to  the  O  obtained  at  758mm,  we  have 
the  following  proportion.  The  volume  at  760mm  will  be  less  than 
at  758mm  ;  or  the  fourth  term  will  be  less  than  the  third  ;  hence  the 
second  must  be  less  than  the  first.  760  :  758  :  :  1450  :  x.  This  would 
give  the  result  dependent  on  pressure  alone. 

Combining  the  two  proportions  in  one  :  — 


1316CC=  1.3161.  It  remains  to  find  the  weight  of  this  gas.  A  liter  of 
H  weighs  0.0896s.  The  vapor  density  of  O  is  16.  Hence  1.3161  O 
will  weigh  1.316  X  16  X  0.0896  =  1.89e. 

(KC103=KC1  +  03) 

From  the  equation  )     122.5  48  V  we  make  a  proportion, 

(        5  *) 

122.5  :5  :  :  48  :x=  1.95,  and  obtain,  as  the  weight  of  O  contained  in 
5s  of  KC1O3,  1.95s.  The  weight  we  actually  obtained  was  1.89*.  This 
leaves  an  error  of  0.06s,  or  a  little  over  4  per  cent  of  error  (0.06  -=-  1.95 
=  0.03+).  The  percentage  of  error,  in  performing  this  experiment, 
should  fall  within  10. 

Some  of  the  liabilities  to  error  are  as  follows  :  — 

1.  Impure  MnO2,  which  sometimes  contains  C.     CO2  is  soluble  in 
H20. 

2.  Solubility  of  O  in  water. 

3.  Escape  of  -gas  by  leakage. 

4.  Moisture  taken  up  by  the  gas. 

5.  Difference  between  the  temperature  of  the  gas  and  that  of  the 
air  in  the  room. 

6.  Errors  in  weighing. 

7.  Want  of  accuracy  in  the  weights  and  scales. 

344.    Hydrogen. 

Experiment  135.  —  Weigh  5s  or  less  of  sheet  or  granulated  Zn, 
and  put  it  into  a   small   flask   provided  with  a   thistle-tube  and  a 


GAS   VOLUMES    AND    WEIGHTS.  203 

delivery-tube.  Cover  the  Zn  with  water,  and  introduce  through 
the  thistle-tube  measured  quantities  of  HC1,  a  few  cubic  centi- 
meters at  a  time.  Collect  the  H  over  water  in  large  flasks,  observ- 
ing the  same  directions  as  in  removing  O.  Weigh  the  water, 
compute  the  volume  of  the  gas,  reduce  it  to  the  standard,  and  obtain 
the  weight,  as  before.  Should  any  Zn  or  other  solid  substance  be 
left,  pour  off  the  water  or  filter  it,  weigh  the  dry  residue,  and  deduct 
its  weight  from  that  of  the  Zn- originally  taken.  Suppose  the  residue 
to  weigh  0.5s.  Make  and  solve  the  proportion  from  the  equation  :  — 

Zn  +  2HC1  =  ZnCl2  +  2H. 
65  2. 

4.5  x. 

Compute  the  percentage  of  errcr,  as  in  the  case  of  O.  If  the  purity 
of  the  IIC1  be  known,  i.e.  the  weight  of  HC1  gas  in  one  cubic  centime- 
ter of  the  liquid,  a  proportion  can  be  made  between  HC1  and  H,  pro- 
vided no  free  HC1  is  left  in  the  flask.  State  any  liabilities  to  error  in 
this  experiment. 

PKOBLEMS. 

(1)  A  gas  occupies  2000CC  when  the  barometer  stands  750mm.   What 
volume  will  it  fill  at  760min? 

(2)  At  750mm  my  volume  of  O  is  4J1.    What  will  it  be  at  730mm  ? 

(3)  At825mm? 

(4)  At200mm? 

(5)  Compute  the  volume  of  a  gas  at  70°,  which  at  30°  is  150CC 

(6)  At  0°  I  have  3000CC  of  O.     What  volume  will  it  occupy  at  100°? 

(7)  I  fill  a  flask  holding  21  with  H.      The  thermometer  indicates 
26°,  the  barometer  762mm.     What  is  the  volume  of  the  gas  at  0°  and 
760mm  9 

If  the  volumes  of  gases  vary  as  above,  it  is  evident  that  their  vapor 
densities  must  vary  inversely.  A  liter  of  H  at  0°  weighs  0.0896. 
What  will  a  liter  of  H  weigh  at  273°?  At  273°  the  one  liter  has  be- 
come two  liters,  one  of  which  weighs  0.0448 (  =  0.0896 -=-2).  The 
vapor  density  of  a  gas  is  inversely  proportional  to  the  temperature. 
Also,  the  vapor  density  is  directly  proportional  to  the  pressure,  since 
a  liter  of  any  gas  under  a  pressure  of  one  atmosphere  is  reduced  to 
half  a  liter  under  two  atmospheres. 


204  GAS    VOLUMES   AND   WEIGHTS. 


PKOBLEMS. 

(1)  Find  the  weight  of  a  liter  of  O  at  0° ;  then  compute  the  weight 
of  a  liter  at  27°. 

(2)  Find  the  weight  of  500CC  of  N2O  at  60°. 

(3)  Of  200ccof  CO  at -5°. 

(4)  A  given  volume  of  O  weighs  0.25s  at  a  pressure  of  750mm ;  find 
the  weight  of  a  like  volume  of  O  at  758mm 


APPENDIX. 

The  Author's  Laboratory  Manual  is  published  by  Ginn  $-  Company. 

APPARATUS. 

Each  pupil  should  be  provided  with  the  following  apparatus.  See  fron- 
tispiece. Apparatus  and  chemicals  can  be  obtained  of  Dr.  A.  P.  Gage, 
Boston ;  minerals  and  metals,  of  Dr.  A.  E.  Foote,  Philadelphia. 


4  wide-mouthed  bottles  (horse-rad- 
ish size),  with  corks. 

1  soda-bottle. 

4  pieces  window-glass  (3  in.  sq.). 

2  pieces  thick  glass  tubing  (20  in. 

long,  \  in.  outside  diam.). 
1  glass  stirring-rod. 

1  glass  funnel  (2J  in.  wide,  60°). 

2  pieces  glass  tubing  (12  in.  long, 

|  in.  diana.). 
1  porcelain  evaporating-dish  (3  in. 

wide). 
1  asbestus  paper  and   1  fine  wire 

gauze  (3  in.  sq.). 


1  iron  (or  tin)  plate. 

1  pair  forceps. 

1  triangular  file  and  1  round  file. 

1  copper  wire  (15  in.  long). 

6  test-tubes,  and  corks  to  fit. 

1  wooden  test-tube  holder. 

1  flask  with  cork  (200CC). 

1  Bunsen  burner  (or  alcohol  lamp). 

1  iron  ring-stand. 

1  piece  rubber  tubing  (18  in.  long, 

|  in.  inside  diam.). 
4  reagent     bottles     (250CC),     HC1, 

HN03,  H,S04,  NH4OH. 
1  pneumatic  trough. 


Wherever  in  this  work  "  Bunsen  burner "  or  "  lamp  "  is  mentioned,  if 
gas  is  not  to  be  had,  an  alcohol  lamp  may  be  substituted. 


GENERAL  APPARATUS. 

The  following  list  includes  apparatus  needed  for  occasional  use :  — 


Metric  rules  (20  or  30cm  long). 
Metric  graduates  (25  or  50CC). 
Metric  graduates  (500CC). 


Scales  with  metric  weights  (1-2008). 

Filter  papers. 

Reagent  bottles  (250  and  500CC). 


206 


APPENDIX. 


Mouth  blowpipes. 

Platinum  wire  and  foil. 

Mortars  and  pestles. 

Test-tube  racks. 

Thistle-tubes. 

Filter-stands. 

Beakers. 

Glass  tubing  (T3^  in.,  J  in.,  and  1  in. 
outside). 

Rubber  tubing  (^  in.,  and  f  in.  in- 
side). 


Hessian  crucibles. 

Porcelain  crucibles. 

Electrolytic  apparatus,  including  2 

or  more  Bunsen  cells. 
Ignition-tubes. 
Steel  glass-cutters. 
Wire-cutters. 
Calcium  chloride  tubes. 
Water  baths. 
Thermometers. 
Barometers,  etc. 


CHEMICALS. 

The  following  estimate  is  for  twenty  pupils :  — 


Alcohol 1  pt. 

Alum  .  . 1  oz. 

Ammonium  chloride  .  .  .  ?]  Ib. 

Ammonium  hydrate  .  .  .  1  Ib. 

Ammonium  nitrate  .  .  .  .  \  Ib. 
Antimony  (powdered  metallic)  \  oz. 

Arsenic  (powdered  metallic)  \  oz. 

Arsenic  trioxide 1  oz. 

Barium  chloride 1  oz. 

Barium  nitrate 1  oz. 

Beeswax  • 1  oz. 

Bleaching-powder  .  .  .  .  \  Ib. 

Bone-black  .  .  .  ...  .  \  Ib. 

Bromine \  Ib. 

Calcium  chloride  .  .  .  .  1  Ib. 

Calcium  fluoride  (powdered)  \  Ib. 

Cannel  coal 1  Ib. 

Carbon  disulphide  .  .  .  .  \  Ib. 

Chlorhydric  acid  .  .  .  .  6  Ib. 

Cochineal 1  oz. 

Copper  (filings) 2  Ib. 

.     .  1  oz. 

.     .  Jib. 

.     .  Jib- 

.    .  1  Ib. 


Copper  nitrate  . 
Copper  oxide  .  . 
Ether  (sulphuric) 
Ferrous  sulphide . 
Ferrous  sulphate 


Indigo \  Ib. 

Iodine 1  oz. 

Iron  (filings  or  turnings)  .     .  1  Ib. 

Lead  (sheet) 4  Ib. 

Lead  acetate    .     .     .     ....  1  oz. 

Lead  nitrate \  Ib. 

Litmus £  oz. 

Litmus  paper 3  sheets. 

Magnesium  ribbon    .     .    »     .  3  ft. 

Manganese  dioxide  .     .'   .     .  2  Ib. 

Mercurous  nitrate    .     .     .     .  \  oz. 

Nitric  acid  .......  3  Ib. 

Oxalic  acid ]  Ib. 

Phosphorus \  Ib. 

Potassium  (metallic)    .     .     .  \  oz. 

Potassium  bromide  .     .     .     .  \  Ib. 

Potassium  dichromate  .     .     .  \  Ib. 

Potassium  chlorate  .     .     .     .  2  Ib. 

Potassium  hydrate  .     .     .     .  \  Ib. 

Potassium  iodide      .     .     .     .  2  oz. 

Potassium  nitrate     .     .     .     .  \  Ib. 

Silver  nitrate 1  oz. 

Sodium \  oz. 

Sodium  carbonate    .     .     .     .  \  Ib. 

Sodium  hydrate 1  Ib. 

Sodium  nitrate \  Ib. 


APPENDIX. 


207 


Sodium  silicate 
Sodium  sulphate 
Sodium  sulphide 
Sodium  thiosulphate 
Sulphur  .     . 


.    .    .    .    Jib. 
v,     .     .    Jib. 
hate     ...     }  Ib. 

Turpentine  (spirits) 
Zinc  (granulated)    .     . 
Zinc  foil      

•     •     j.y«. 
.     .     J  Ib. 
.     .     2  Ib. 
.    3  ft 

.     2  Ib. 

Sulphuric  acid 

.  12  Ib. 

Additional  Material. 
These  substances  are  best  obtained  of  local  dealers. 


Calcium  carbonate  (marble),     1  Ib. 
Calcium  oxide  (unslaked  lime),l  Ib. 

Charcoal 1  Ib. 

Sheet  lead  .  .     4  Ib. 


Molasses      ...          .     .     .  1  pt. 

Sodium  chloride   (fine)     .     .  1  Ib. 

Sodium  chloride  (coarse)      .  1  Ib. 

Sugar }  Ib. 


Argillite, 

Arsenic, 

Arsenopyrite, 

Barite, 

Calcite, 

Cassiterite, 

C  h  alco  pyrite , 

Chalk, 

Cinnabar, 

Copper  (native), 

Corundum, 

Dolomite, 

Emery, 

Feldspar, 

Flint, 

Galenite, 

Granite, 

Graphite, 

Gypsum, 

Hematite, 


FOR   EXAMINATION. 

Those  in  heavy  type  are  most  important. 
Rocks  and  Minerals. 


Hornblende, 

Jasper, 

iJimonite, 

Magnesite, 

Magnetite, 

Malachite, 

Meerschaum, 

Mica, 

Obsidian, 

Orpiment, 

Pyrite, 

Quartz, 

Realgar, 

Sand, 

Serpentine, 

Siderite, 

Sphalerite, 

Talc, 

Zincite. 


208 


APPENDIX. 


Metals  and  Alloys. 


Aluminium, 

Aluminium  bronze, 
Bell  metal, 
Brass, 
Bronze, 
Copper, 

Galvanized  iron, 
German  silver, 
Iron  (wrought), 


Iron  (cast), 

Pewter, 

Solder, 

Steel, 

Type  metal, 

Tin  foil, 

Tin  (bright  plate  and  terne  plate), 

Zinc  (sheet). 


Copper  acetate, 
Copper  arsenite, 
Copper  nitrate, 
Copper  sulphate, 
Lead  dioxide, 
Lead  protoxide, 


Additional   Compounds  for  Examination. 

Lead  carbonate, 
Red  lead, 
Magnesia  alba, 
Smalt, 
Vermilion. 


TABLE   OF   SOLUTIONS. 

Number  of  grams  of  solids  to  be  dissolved  in  500CC  of  water. 


AgNO3 25 

BaCl2 50 

Ba(N03)2   . 30 

CaCl2 60 

Ca(OH)2 saturated 

CaSO4 saturated 

CuCl2 .     50 

Cu(N03)2 50 

FeS04 50 

HgCl2 ...     30 

HgNO3 25  +  25HN03 

Other  solutions     , 


K2A1,(S04)4 

KBr  .     .  . 

K2Cr2O7  . 

KI     .     .  . 

KOH      .  . 

Na2CO3  .  . 

NaOH    .  . 

Na,S203.  . 

NH4NO3  . 


50 

25 

50 

.....  25 

60 

50 

..;..-.    .  60 

.     ,     .  saturated 

.   .?    .    V    .  50 

Pb(C2H3O2)2 50 

Pb(NO3)2 50 

,     saturated. 


Indigo  solution  (sulphindigotic  acid)  is  prepared  by  heating  for  sev- 
eral hours  over  a  water  bath,  a  mixture  of  ten  parts  of  H2SO4  with  one  of 
indigo,  and,  after  letting  it  stand  twenty-four  hours,  adding  twenty  parts 
of  water  and  filtering. 


INDEX. 


[NUMBERS  REFER  TO  PAGES.] 


A. 

Acid  reaction,  52. 

salts,  55. 
Acids,  45,  49. 

Naming,  50. 
Alcohol,  ethyl,  184. 
Alcohols,  177. 
Alizarine,  175. 
Alkali,  52. 

belt,  140. 

metals,  52. 

Alkaline  reaction,  52. 
Alloys,  136. 
Allotropy,  33,  84,  117. 
Alumina,  134, 153. 
Aluminium,  151. 

bronze,  137, 151. 
Amalgams,  137. 
Ammonia,  67,  87. 
Ammonium  compounds,  145. 

hydrate,  67. 
Analysis,  6. 

Water,  44. 
Anhydride,  50. 
Anhydrite,  149. 
Aniline  dyes,  179. 
Aqua  regia,  61. 
Argillite,  151. 
Arsene,  127. 
Arsenic,  126. 

trioxide,  128. 
Arsenopyrite,  128. 
Atmosphere,  Chemistry  of,  81 
Artificial  stone,  131. 
Atom,  6,  9. 
Atomic  weight,  111. 

volume,  112. 
Avogadro's  law,  8,  46. 
Azurite,  164. 


Bases,  45,  51,  67. 
Basicity  of  acids,  55. 
Beer,  185. 
Bell-metal,  136. 
Benzine,  177. 
Bicarbonate  of  sodium,  142. 

of  potassium,  143. 
Binary,  11. 
Bivalent,  39. 
Blasting  powder,  142. 
Bleaching,  99-101,  119. 
Bonds,  38. 
Bone-black,  34. 
Brass,  137. 
Bread,  194. 
Bricks,  133. 
Bromhydric  acid,  58. 
Bromine,  101. 

compounds,  102. 
Bronze,  136. 
Butter,  187. 

C. 

Calcium,  146. 

carbonate,  146. 

hydrate,  70, 147. 

light,  28. 

silicate,  132. 

sulphate,  149. 
Carbon,  5,  6,  32. 

allotropic  forms,  33. 

a  reducing  agent,  36. 

a  disinfectant,  37. 

an  absorber  of  gases,  37, 

Combustion  of,  19. 

dioxide,  19,  79,  87. 

protoxide,  77. 


210 


INDEX. 


Carbonates,  83. 
Carbonic  anhydride,  80. 

acid,  80. 

Carbo-hydrates,  189. 
Cassiterite,  163. 
Caustic  potash,  70. 

soda,  69. 
Caves,  148. 
Celluloid,  192. 
Cellulose,  191. 
Centimeters,  1. 
Chalcopyrite,  164. 
Chalk,  171. 
Charcoal,  5,  34. 
Chemical  activity,  20. 

change,  4,  7. 

union,  9, 13. 
Chemism,  5,  6. 
Chemistry,  3. 

New  theory  of,  200. 

of  life,  196. 

of  vegetation,  123,  197. 
China-ware,  133. 
Chlorhydric  acid,  56. 
Chlorine,  98. 
Chloroform,  178. 
Choke  damp,  80. 
Cinnabar,  165. 
Clay,  15L 
Coal,  Mineral,  35. 
Coal-gas,  182. 
Cochineal,  175. 
Coefficient,  11. 
Coke,  34. 
Colloids,  131. 
Combustible,  95,  96. 
Combustion  of  metals,  99. 

under  water,  122. 
Compound,  4,  5,  6. 
Condensation,  Temperature  of,  93,  97. 

of  gases,  47,  114. 
Conservation,  198. 
Cooking  soda,  142. 
Copper,  164. 

Deposition  of,  42. 
Copperas,  160. 
Corks,  To  perforate,  15. 
Corundum,  151. 
Crith,  108. 

Cryolite,  105, 133.  .  »• 

Crystalloids,  131, 


Crystals,  173. 
Cyanhydric  acid,  144. 
Cyanide  of  potassium,  144. 


D. 

Davy  lamp,  94. 
Deliquescence,  173. 
Deoxidizing  agent,  36. 
|    Deoxidation  in  plants,  82. 
Dextrin,  192. 
Dextrose,  190. 
Dialysis,  131. 
Diamond,  33. 
Dibasic  acid,  55. 
Diffusion  of  gases,  114. 
Digestion,  194. 
Diseases,  195. 
Disinfection,  37,  85,  99. 
Dissociation,  18. 
Distillation,  88. 
Distilled  liquor,  184. 
pivalent,  39. 

Divisibility  of  matter,  3,  4. 
Dolomite,  150. 
Downward  displacement,  (. 
Drummond  light,  28. 
Dyad,  39. 
Dynamite,  187. 


Earth,  A  cooling,  199. 

Interior  of,  173. 
Efflorescence,  173. 
Electro-chemical  relation,  41. 

table,  43. 

Electrolysis,  44. 
Elements,  5,  10. 

Table  of,  12. 

Per  cent  of,  173. 
Emery,  151. 
Energy,  151. 
Epsom  salt,  151. 
Etching  glass,  59. 
Ethers,  178. 
Evolution,  199. 
Expert  analysis,  127. 
Explosions,  27,  96. 
Exponents,  11. 


INDEX. 


211 


Fats,  186. 
Feldspar,  151, 172. 
Fermentation,  193. 

Lactic,  194. 

Fermented  liquor,  184. 
Ferrous  and  ferric  salts,  159. 

sulphate,  160. 

sulphide,  160. 
Filter  paper,  3. 
Filtrate,  3. 
Flame,  Chemistry  of,  91. 

Bunsen,  92. 

Candle,  91. 

Light  and  heat  of,  93. 

Oxidizing  and  reducing,  94. 
Fluorhydric  acid,  58. 
Fluorine,  105. 
Fluorite,  105. 
Food  of  man,  197. 

of  plants,  196. 
Fuchsine,  4. 

G. 

Galena,  161. 
Galvanized  iron,  153. 
Gas-carbon,  34. 
Gases,  Diffusion  of,  114. 

Liquefaction  and  solidification  of,  115 
Gas,  Illuminating,  180. 

Natural,  183. 

Gaseous  molecule,  8,  46, 108. 
Gasoline,  177. 

Gas  volumes  and  weights,  201. 
German  silver,  137. 
Germs  of  disease,  87, 195. 
Glass,  132. 

Etching,  59. 

manipulation,  14, 15. 
Glucose,  190. 
Glycerin,  186. 
Gneiss,  171. 
Gold,  169. 
Graduate,  1. 
Granite,  172. 
Graphite,  34. 
Graphic  symbols,  39, 176. 
Gun  cotton,  192. 

metal,  136. 
Gunpowder,  144. 


Halogens,  106. 

Acids  and  salts  of,  107. 
Heat,  Absorption  and  disengagement  of, 

97. 

Hematite,  154. 
Hexad,  39. 
Honey,  189. 
Hydrate,  43. 
Hydrogen,  24. 

quantitatively,  202. 

sulphide,  120. 

phosphide,  125. 

sodium  carbonate,  142. 
Hydr^bromic  acid,  58. 
Hydrocyanic  acid,  144. 
Hydrofluoric  acid,  58. 
Hydriodic  acid,  58. 
Hydrochloric  acid,  57. 


Ignition  tubes,  14. 
Illuminating  gas,  180. 
Infection,  195. 
Indigo,  175. 
lodihydric  acid,  58. 
Iodine,  103. 

lodo-starch  paper,  84, 104. 
Iron,  154. 

Combustion  of,  20. 

rust,  21. 

tetroxide,  20. 


Kaolin,  115:5. 
Kerosene,  177. 


Lactic  fermentation,  194. 
Lamp-black,  34. 
La  Place  theory,  199. 
Lead,  161. 

compounds,  162. 

Deposition  of,  42. 

poisons,  162. 
Length,  1. 
Levulose,  190, 


212 


INDEX. 


-Liebig's  condenser,  88. 
Lignite,  11. 
Lime,  71,  146. 

Superphosphate  of,  123. 
Limonite,  154. 
Litmus,  49,  52. 
Lunar  caustic,  166. 
Luster,  41,  135. 


M. 

Madder,  175. 
Magnesia,  151. 
Magnesite,  150. 
Magnesium,  150. 
Magnetite,  154. 
Malachite,  164. 
Manipulation,  14. 
Marble,  148. 
Marsh-gas  series,  176. 
Marsh's  test,  126. 
Mass,  4,  5. 
Matches,  124. 
Matter,  Division  of,  3. 
Meerschaum,  150. 
Mercury,  165. 
Metals,  41,  135. 
Metamorphism,  146. 
Metathesis,  7. 
Metric  system,  1. 
Mica,  172. 
Microcrith,  108. 
Mineral  growth,  196. 
Minerals,  172. 
Mixture,  5,  86. 
Molasses,  189. 
Molecule,  4,  5,  8. 
Molecular  differences,  174. 

weight,  109. 

volume,  112. 
Monad,  39. 
Monobasic,  55. 
Monovalent,  39. 
Muriatic  acid,  57. 


N. 

Naphtha,  177. 
Naphthol-scarlet,  176. 
Natural  gas,  183. 
Neutralization,  53. 


Nitric  acid,  60. 
Nitrogen,  22. 

dioxide,  73. 

monoxide,  72. 

pentoxide,  74. 

tetroxide,  73. 

trioxide,  74. 
Nitro-glycerin,  187. 
Nitro-hydrochloric  acid,  62. 
Nitrous  oxide,  73. 
Non-metals,  135. 
Nordhausen  sulphuric  acid,  66 
Normal  salts,  55. 

O. 

Obsidian,  172. 
Oils,  186. 
Oil-fines,  179. 
Olein,  186. 

Oleomargarine,  187. 
Organic  chemistry,  174. 
Orpiment,  128. 
Oxidation  in  the  system,  80. 

in  water,  81. 
Oxidizing  agent,  36. 
Oxide,  13. 
Oxygen,  17. 

a  supporter  of  life,  81. 

quantitatively,  201. 
Oxy-hydrogen  blow-pipe,  28. 
Ozone,  84. 

P. 

Palmitin,  186. 
Parchment,  191. 
Paris  green,  165. 
Peat,  34. 
Pentad,  39. 
Pewter,  137. 
Petroleum,  176. 
Philosopher's  lamp,  26. 
Phosphates,  123. 
Phosphene,  125. 
Phosphorus,  122. 

Oxides  of,  20. 

Red,  124. 

Photography,  167. 
Pig-iron,  154. 

Plant-food,  82, 123, 145, 190, 19A 
Plaster  of  Paris,  149. 


INDEX. 


Platinum,  168. 
Plumbago,  34. 
Porcelain  and  pottery,  133, 
Potassium,  143. 

chlorate,  144. 

cyanide,  144. 

hydrate,  70. 
Proportion  by  weight,  29. 

Law  of  definite,  75. 

Law  of  multiple,  76. 
Prefixes,  13. 
Pseudo-triad,  40. 
Purple  of  Cassius,  133. 
Putrefaction,  194. 
Pyrite,  160. 


Quantitative  work,  201,  202. 
Quantivalence,  38. 
Quartz,  172. 

K. 

Radical,  40,  43. 
Reaction,  25. 

Acid  and  alkaline,  52. 
Realgar,  128. 
Reducing  agent,  36. 
Refractory  substances,  134. 
Residue,  3. 
Rhigoline,  177. 
Rocks,  171. 


Salts,  45,  53. 

Acid  and  normal,  55. 

Naming,  54. 
Saccharine,  175. 
Sandstone,  171. 
Saponification,  187. 
Saprophytes,  194. 
Schist,  171. 
Sea-weeds,  104. 
Serpentine,  150. 
Shale,  171. 
Siderite,  154. 
Silica,  130. 
Silicates,  131. 

Artificial,  132. 
Silicic  acid,  131. 
Silicon,  130. 


Silver,  165. 

Salts  of,  166. 
Slag,  156. 
Slate,  171. 
Smalt,  132. 
Smithsonite,  153. 
Soap,  187. 
Soda  water,  82. 
Sodium,  138. 

carbonate,  140. 

chloride,  138. 

hydrate,  69, 142. 

nitrate,  142. 

silicate,  131. 

sulphate,  139. 
Soils,  172. 
Solubility,  3. 
Solution,  3,  4. 
Solvent,  3. 
Specific  gravity,  108. 
Speculum-metal,  136. 
Sphalerite,  153. 

Spontaneous  combustion,  96,  97, 12ii. 
Stalactite,  148. 
Stalagmite,  148. 
Starch,  190. 

test,  103. 
Stearin,  186. 
Steel,  156. 
Sucrose,  189. 
Sublimate,  103. 
Sublimation,  103. 
Sugars,  189. 
Sulphur,  116. 

compounds,  119. 
Sulphuretted  hydrogen,  121. 
Sulphuric  acid,  63-66. 

Fuming,  66. 

Superphosphate  of  lime,  123. 
Supporter  of  combustion,  95,  99. 
Symbols,  10. 
Synthesis,  6. 


T. 

Talc.  150. 

Temperature,  Critical,  115. 

Lowest,  115. 

of  combustion,  93,  97, 152. 

of  the  body,  81. 
Terue  plate,  162. 


214 


INDEX. 


Tetrad,  39. 
Theories,  199. 
Tin,  163. 
Triad,  39. 
Tribasic  acid,  56. 
Turf,  35. 
Type-metal,  137. 


U. 

Union  by  weight,  29. 

by  volume,  46. 
Upward  displacement,  26. 


V. 

Valence,  38. 
Vapor  density,  108. 
Vermilion,  165. 
Vitriols,  153, 160, 165. 
Volume,  Metric,  1. 
Molecular,  64. 


W. 

Water,  Chemistry  of, 
Electrolysis  of,  44. 


Water,  Hard,  147. 
Pure,  88. 
River,  90. 


Spring,  90. 

in  air,  87. 

of  crystallization,  139. 
Water-gas,  78. 
Water-glass,  i31. 
Weight,  2. 

Least  combining,  111. 

of  compounds,  29. 
White  paint,  162. 
Wines,  185. 
Wood's  metal,  137. 
Woulff  bottles,  56. 
Wrought-iron,  157. 


Y. 


Yeast,  193. 


Zinc  and  its  compounds,  153. 
Zincite,  153. 
Zylonite,  192. 


NATURAL  SCIENCE. 


Elements  of  Physics. 


A  Text-book  for  High  Schools  and  Academies.  By  ALFRED  P.  GAGE, 
A.M.,  Instructor  in  Physics  in  the  English  High  School,  Boston.  12mo. 
424  pages.  Mailing  Price,  $1.25;  Introduction,  $1.12. 


rTlHIS  treatise  is  based  upon  the  doctrine  of  the  conservation  of 
energy,  which  is  made  prominent  throughout  the  work.  But 
the  leading  feature  of  the  book  —  one  that  distinguishes  it  from 
all  others  —  is,  that  it  is  strictly  experiment-teaching  in  its  method ; 
i.e.,  it  leads  the  pupil  to  "  read  nature  in  the  language  of  experi- 
ment." So  far  as  practicable,  the  following  plan  is  adopted :  The 
pupil  is  expected  to  accept  as  fact  only  that  which  he  has  seen  or 
learned  by  personal  investigation.  He  himself  performs  the  larger 
portion  of  the  experiments  with  simple  and  inexpensive  apparatus, 
such  as,  in  a  majority  of  cases,  is  in  his  power  to  construct  with  the 
aid  of  directions  given  in  the  book.  The  experiments  given  are 
rather  of  the  nature  of  questions  than  of  illustrations,  and  precede 
the  statements  of  principles  and  laws.  Definitions  and  laws  are  not 
given  until  the  pupil  has  acquired  a  knowledge  of  his  subject  suffi- 
cient to  enable  him  to  construct  them  for  himself.  The  aim  of  the 
book  is  to  lead  the  pupil  to  observe  and  to  think. 


Wm.  Noetling,  State  Normal 
School,  Bloomsburg,  Pa. :  I  know  of 
no  other  work  on  the  subject  that 
I  can  so  unreservedly  recommend  to 
all  wide-awake  teachers  as  this. 

Benj.  F.  Thomas,  Prof,  of  Physics, 
Ohio  State  University :  I  have  used 
it  with  preparatory  classes  for  sev- 
eral years  with  satisfaction.  I  re- 
gard it  as  the  best  for  class-room 
work. 


H.   Wilson    Harding,    Prof,    of 

Physics,  Lehigh  University :  I  be- 
lieve Gage's  Elements  of  Physics  to 
be  based  on  the  true  method  of  study- 
ing that  branch  of  science,  —  that  of 
practical  work  in  the  laboratory  by 
the  student  himself. 

C.  F.  Emerson,  Prof,  of  Physics, 
Dartmouth  College :  It  takes  up  the 
subject  on  the  right  plan,  and  pre- 
sents it  in  a  clear  yet  scientific  way. 


100  NATURAL   SCIENCE. 

Introduction  to  Physical  Science. 

By  A.  P.  GAGE,  Instructor  in  Physics  in  the  English  High  School,  Bos- 
ton, Mass.,  and  author  of  Elements  of  Physics,  etc.  12mp.  Cloth. 
viii  +  353  pages.  With  a  color  chart  of  spectra,  etc.  Mailing  price 
$1.10;  for  introduction,  $1.00- 

rpHE  constantly  increasing  popularity  of  Gage's  Elements  of 
Physics  has  created  a  demand  for  an  easier  book,  on  the  same 
plan,  suited  to  schools  that  can  give  but  a  limited  time  to  the 
study.  The  Introduction  to  Physical  Science  meets  this  demand. 

In  a  text-book,  the  first  essentials  are  correctness  and  accuracy. 
It  is  believed  that  the  Introduction  will  stand  the  closest  expert 
scrutiny.  Especial  care  has  been  taken  to  restrict  the  use  of  scien- 
tific terms,  such  as  force,  energy,  power,  etc.,  to  their  proper  signifi- 
cations. Terms  like  sound,  light,  color,  etc.,  which  have  commonly 
been  applied  to  both  the  effect  and  the  agent  producing  the  effect, 
have  been  rescued  from  this  ambiguity. 

Recent  advances  in  physics  have  been  faithfully  recorded,  and 
the  relative  practical  importance  of  the  various  topics  has  been 
taken  into  account.  Among  the  new  features  are  a  full  treatment 
of  electric  lighting,  and  descriptions  of  storage  batteries,  methods 
of  transmitting  electric  energy,  simple  and  easy  methods  of  mak- 
ing electrical  measurements  with  inexpensive  apparatus,  the  com- 
pound steam-engine,  etc.  Static  electricity,  now  generally  regarded 
as  of  comparatively  little  practical  importance,  is  treated  briefly ; 
while  dynamic  electricity,  the  most  promising  physical  agent  of 
modern  times,  is  placed  in  the  clearest  light  of  our  present 
knowledge. 

The  wide  use  of  the  Elements  under  the  most  varied  conditions, 
and,  in  particular,  the  author's  own  experience  in  teaching  it,  have 
shown  how  to  improve  where  improvement  was  possible.  The 
style  will  be  found  suited  to  the  grades  that  will  use  the  book. 
The  experiments  are  of  practical  significance,  and  simple  in  manip- 
ulation. The  Introduction  is  even  more  fully  illustrated  than  the 
Elements. 

The  Introduction,  like  the  author's  Elements,  has  this  distinct 
and  distinctive  aim, — to  elucidate  science,  instead  of  "populariz- 
ing" it;  to  make  it  liked  for  its  own  sake,  rather  than  for  its  gild- 


NATURAL    SCIENCE. 


101 


ing  and  coating;  and,  while  teaching  the  facts,  to  impart  the  spirit 
of  science,  that  is  to  say,  the  spirit  of  our  civilization  a,nd  progress. 


Alexander  Macfarlane,  Prof,  of 

Physics,  University  of  Texas :  I  con- 
sider that  the  principal  features  of 
the  book — its  clearness  and  accuracy 
of  statement,  its  information  being 
up  to  date,  and  the  practical  nature 
of  the  instruction  —  make  it  valua- 
ble as  a  first  text-book  in  Physics  in 
high  schools  and  academies,  and  es- 
pecially for  those  institutions  that 
prepare  for  the  universities. 

I.  Thornton  Osmond,  Prof,  of 
Physics,  State  College,  Pa. :  For 
selection  of  matter  and  method  of 
treatment,  for  comprehensiveness, 
brevity,  clearness,  and  accuracy,  for 
the  simplicity  and  value  of  experi- 
ments, it  was,  and  yet  is,  unrivalled 
as  a  text-book  for  high  school  and 
academic  work. 

George  E.  Gay,  Prin.  of  High 
School,  Maiden,  Mass.:  With  the 
matter,  both  the  topics  and  their  pre- 
sentation, I  am  better  pleased  than 
with  any  other  Physics  I  have  seen. 

J.  P.  Naylor,  Prof,  of  Physics,  De 
Pauw  University:  In  its  scientific 


spirit,  and  in  accuracy  and  clearness 
of  statements  of  principles,  I  know 
nothing  that  is  its  superior.  The  ex- 
tent to  which  the  work  is  carried  i« 
also  about  what  can  be  well  done  in 
the  time  our  schools  usually  have  to 
give  to  the  subject.  It  is  used  in 
preparatory  work  at  this  University 
as  the  best  we  can  get. 

0.  C.  Kinyon,  Teacher  of  Physics 
in  High  School,  Syracuse,  N.  Y. :  It 
not  only  insures  an  interest  in  the 
study  but  tends  to  thoroughly  arouse 
those  powers  of  observation,  the  de- 
velopment of  which  is  the  especial 
province  of  scientific  study. 

B.  C.  Hinde,  Professor  Natural 
Science,  Trinity  College,  N.  C. :  I 
have  used  Gage's  Introduction  to 
Physical  Science  for  two  years,  and 
I  consider  it  the  best  book  published 
for  its  purpose.  It  is  strictly  in 
accord  with  the  best  modern  teach- 
ing of  Physics.  I  have  made  it  a 
point  to  call  the  attention  of  my  stu- 
dents to  this  book  that  they  may  use 
it  in  their  teaching. 


Physical  Laboratory  Manual  and  Note  Booh. 

By  A.  P.  GAGE,  Instructor  in  Physics  in  English  High  School,  Boston, 
and  author  of  Elements  of  Physics,  Introduction  te  Physical  Science, 
etc.  12mo.  Boards,  xii  +  244  pages.  By  mail,  45  cents  ;  for  introduction, 
35  cents. 


manual  has  been  prepared  especially  to  accompany  the 
author's  text-books,  but  is  adapted  for  use  in  connection  with 
any  good  text-book  on  the  subject.  The  left-hand  page  contains 
cuts  of  apparatus  to  be  used,  directions  for  performing  experiments 
(upwards  of  one  hundred  in  number),  and  questions  to  be  an- 
swered in  connection  with  the  experiments.  Suggestions  to 
teachers,  the  needed  tables,  etc.,  are  provided  at  the  beginning. 
The  right-hand  pages  are  left  blank  for  the  pupil's  notes. 


102 


NATURAL    SCIENCE. 


A  Students'  Manual  of  a  Laboratory  Course  in 

Physical  Measurements. 

By  WALLACE  CLEMENT  SABINE,  A.M.,  Instructor  in  Harvard  Univer- 
sity. 8vo.  Cloth,  ix+126  pages.  Mailing  price,  $1.36;  for  intro- 
duction, $1.25. 


manual,  which  is  intended  for  use  in  supplementing  col- 
lege courses  in  physics,  contains  an  outline  of  seventy  experi- 
ments in  mechanics,  sound,  heat,  light,  magnetism  and  electricity, 
arranged  with  special  regard  to  a  systematic  and  progressive  de- 
velopment of  the  subject.  The  description  of  each  experiment  is 
accompanied  by  a  brief  statement  of  the  physical  principles  and 
definitions  involved,  and  a  proof  of  necessary  formulae. 

Le  Koy  C.  Cooley,  Professor  of 
Physics,  Vassar  College  :  I  have  ex- 
amined it  and  am  ready  to  com- 
mend it. 

Fernando  Sanford,  Professor  of 
Physics,  Leland  Stanford  Junior 
University  :  I  like  the  book  very 


much.  It  is  better  adapted  to  the 
kind  of  work  which  I  am  trying  to 
do  than  any  other  book  I  have  seen. 
J.  F.  Woodhull,  Professor  of  Sci- 
ence, Teachers'  College,  New  York: 
I  find  Sabine's  Laboratory  Manual 
a  thoroughly  good  thing. 


High  School  Laboratory  Manual  of  Physics. 

By  DUDLEY  G.  HAYS,  CHARLES  D.  LOWRY,  and  AUSTIN  C.  RISHEL, 
Teachers  of  Physics  in  the  Chicago  High  Schools.  8vo.  Cloth. 
iv+154  pages.  Mailing  price,  00  cents;  for  introduction,  50  cents. 

manual  has  been  written :  First,  to  present  a  logically 
arranged  course  of  experimental  work  covering  the  ground 
of  Elementary  Physics.  Second,  to  provide  sufficient  laboratory 
work  to  meet  college  entrance  requirements.  Tt  contains  equiva- 
lents of  most  of  the  exercises  in  the  Harvard  Pamphlet. 

The  experiments  are  largely  quantitative,  but  qualitative  work 
is  introduced.  Apparatus  has  been  chosen  that  may  in  most 
cases  be  duplicated  at  small  cost.  Special  care  has  been  taken  to 
make  details  of  work  clear,  and  to  instruct  the  pupil  in  the 
methods  of  making  generalizations  from  his  results.  Alternate 
pages  are  blank  for  convenience  in  taking  notes. 


W.  S.  Jackman,  Teacher  of  Science, 
Cook  Co.  Normal  School,  Englewood, 
HI. :  It  is  a  most  excellent  manual 


and  I  believe  it  meets  the  needs  of 
high  schools  on  this  subject  better 
than  any  other  book  I  have  seen. 


NATURAL    SCIENCE. 


103 


Introduction  to  Chemical  Science. 

By  R.  P.  WILLIAMS,  Instructor  in  Chemistry  in  the  English  High 
School,  Boston.  12mo.  Cloth.  216  pages.  By  mail,  90  cents;  for 
introduction,  80  cents. 

work  is  strictly,  but  easily,  inductive.  The  pupil  is  stimu- 
lated  by  query  and  suggestion  to  observe  important  phenomena, 
and  to  draw  correct  conclusions.  The  experiments  are  illustrative, 
the  apparatus  is  simple  and  easily  made.  Such  elements,  com- 
pounds, and  experiments  as  pupils  have  no  use  for,  are  omitted. 
The  nomenclature,  symbols,  and  writing  of  equations  are  made 
prominent  features.  In  descriptive  and  theoretical  chemistry,  the 
arrangement  of  subjects  is  believed  to  be  especially  superior  in 
that  it  presents,  not  a  mere  aggregation  of  facts,  but  the  science 
of  chemistry.  Brevity  and  concentration,  induction,  clearness, 
accuracy,  and  a  legitimate  regard  for  interest,  are  leading  charac- 
teristics. The  treatment  is  full  enough  for  any  high  school  or 
academy. 

Though  the  method  is  an  advanced  one,  it  has  been  so  simplified 
that  pupils  experience  no  difficulty,  but  rather  an  added  interest, 
in  following  it ;  the  author  himself  has  successfully  employed  it  in 
classes  so  large  that  the  simplest  and  most  practical  plan  has  been 
a  necessity. 


H.  T.  Fuller,  Pres.  of  Polytechnic 
Institute,  Worcester,  Mass. :  It  is 
clear,  concise,  and  suggests  the  most 
important  and  most  significant  ex- 
periments for  illustration  of  general 
principles. 

Thos.  C.  Van  Nu'ys,  Prof,  of  Chem- 
istry, Indiana  University,  Sloom- 
ington,  Ind.:  I  consider  it  an  excel- 
lent work  for  students  entering  upon 
the  study  of  chemistry. 

G.  W.  Shaw,  Prof,  of  Chemistry, 
Pacific  University,  Forest  Grove, Or.: 
I  am  especially  pleased  with  it  as 
filling  a  place  which  no  other  work 
has  filled.  - 


W.  J.  Martin,  Prof,  of  Chemistry, 
Davidson  College,  N.C. :  I  think  it 
is  one  of  the  most  admirable  little 
text-books  I  have  ever  seen. 

Wm.  F.  Langworthy,  Teacher  of 
Chemistry,  Colgate  Academy,  Hamil- 
ton, JV.  Y. :  I  am  much  pleased  that 
we  introduced  it. 

T.  H.  Norton,  Prof,  of  Chemistry, 
Cincinnati  University,  0. :  Its  clear- 
ness, accuracy,  and  compact  form 
render  it  exceptionally  well  adapted 
for  use  in  high  and  preparatory 
schools.  I  shall  warmly  recommend 
it  for  use  whenever  the  effort  is  made 
to  provide  satisfactory  training  in 


104 


NATURAL   SCIENCE. 


accordance  with  the  requirements  for 
admission  to  the  scientific  courses  of 
the  University. 

C.  F.  Adams,  Teacher  of  Science, 
High  School,  Detroit,  Mich. :  I  have 
carried  two  classes  through  Wil- 
liam's Chemistry,  and  the  book  has 
surpassed  my  highest  expectations. 
It  gives  greater  satisfaction  with 
each  succeeding  class. 

C.  K.  Wells,  formerly  Supt.  of 
Schools,  Marietta,  0.:  The  book 
bears  acquaintance  the  best  of  any 
book  of  .like  character  that  I  have 
ever  examined. 

W.  T.  Mather,  Teacher  of  Science, 
Williston  Seminary,  Fasthampton, 
Mass. :  I  have  used  the  book  in  the 
laboratory  very  successfully.  I  can 
heartily  commend  it  for  the  method 
used  and  the  clear  and  concise  treat- 
ment of  the  subject. 

J.  W.  Simmons,  Supt.  Schools, 
Owosso,  Mich. :  The  proof  of  the 
merits  of  a  text-book  is  found  in  the 
crucible  of  the  class-room  work. 


There  are  many  chemistries,  and 
good  ones;  but,  for  our  use,  this 
leads  them  all.  There  is  enough  and 
not  too  much  in  the  work.  It  is 
stated  in  language  plain,  interesting 
and  not  misleading.  A  logical  order 
is  followed,  and  the  mind  of  the 
student  is  at  work  because  of  the 
many  suggestions  offered.  Our  high 
schools  have  no  province  in  chemistry 
beyond  the  basic  facts.  Too  many 
text-books  go  beyond  this  introduc- 
tory field,  but  not  far  enough  to  clear 
away  the  mists  that  arise.  The  stu- 
dent's mind  is  lumbered  with  things 
of  which  he  sees  no  application.  It 
is  not  education  but  the  barest  kind 
of  stuffing. 

We  use  Williams's  work  and  the 
results  are  all  we  could  wish.  There 
is  plenty  of  chemistry  in  the  work 
for  any  of  our  high  schools.  The 
above  opinion  is  based  upon  an  ex- 
perience of  twelve  years  as  teacher 
of  chemical  science. 


Laboratory  Manual  of  General  Chemistry. 

By  R.  P.  WILLIAMS,  Instructor  in  Chemistry,  English  High  School,  Bos- 
ton, and  author  of  Introduction  to  Chemical  Science.  12mo.  Boards, 
xvi  +  200  pages.  By  mail,  30  cents ;  for  introduction,  25  cents. 

rpHE  book  contains  one  hundred  experiments  in  general  chemistry 
and  qualitative  analysis,  blanks  opposite  each  for  pupils  to 
take  notes,  laboratory  rules,  complete  tables  of  symbols,  with 
chemical  and  common  names,  reagents,  solutions,  chemicals,  and 
apparatus,  and  the  plan  of  a  model  laboratory.  Minute  directions, 
and  suggestions  designed  to  help  the  pupils  observe  and  draw 
inferences,  characterize  each  experiment. 


W.  M.  Stine,  Prof,  of  Chemistry, 
Ohio  University,  Athens,  0.:  It  is  a 
work  that  has  my  heartiest  endorse- 
ment. I  consider  it  thoroughly  peda- 


gogical in  its  principles,  and  its  use 
must  certainly  give  the  student  the 
greatest  benefit  from  his  chemical 
drill. 


JSATURAL  SCIENCE. 


105 


Young's  Lessons  in  Astronomy. 


Including  urauography.  By  CHARLES  A.  YOUNG,  Ph.D.,  LL.D.,  Pro- 
fessor of  Astronomy  in  the  College  of  New  Jersey  (Princeton),  and 
author  of  A  General  Astronomy,  Elements  of  Astronomy,  etc.  12mo. 
Cloth.  Illustrated,  ix  +  357  pages,  exclusive  of  four  double-page  star 
maps.  By  mail,  $1.30;  for  introduction,  $1.20. 


volume  has  been  prepared  for  schools  that  desire  a  brief 
course  free  from  mathematics.  It  is  based  upon  the  author's 
Elements  of  Astronomy,  but  many  condensations,  simplifications, 
and  changes  of  arrangement  have  been  made.  In  fact,  everything 
has  been  carefully  worked  over  and  rewritten  to  adapt  it  to  the 
special  requirements.  Great  pains  has  been  taken  not  to  sacrifice 
accuracy  and  truth  to  brevity,  and  no  less  to  bring  everything 
thoroughly  down  to  date.  The  latest  results  of  astronomical  in- 
vestigation will  be  found  here.  The  author  has  endeavored,  too, 
while  discarding  mathematics,  to  give  the  student  a  clear  under- 
standing and  a  good  grasp  of  the  subject.  As  a  body  of  informa- 
tion and  as  a  means  of  discipline,  this  book  will  be  found,  it  is 
believed,  of  notable  value.  The  most  important  change  in  the 
arrangement  of  the  book  has  been  in  bringing  the  Uranography, 
or  constellation  tracing,  into  the  body  of  the  text  and  placing  it 
near  the  beginning,  a  change  in  harmony  with  the  accepted  prin- 
ciple that  those  whose  minds  are  not  mature  succeed  best  in  the 
study  of  a  new  subject  by  beginning  with  what  is  concrete  and 
appeals  to  the  senses,  rather  than  with  the  abstract  principles. 
Brief  notes  on  the  legendary  mythology  of  the  constellations  have 
been  added  for  the  benefit  of  such  pupils  as  are  not  likely  to 
become  familiar  with  it  in  the  study  of  classical  literature. 


M.  W.  Harrington,  Chief  of  U.  S. 
Weather  Bureau,  Washington,  D.C. : 
I  have  been  much  pleased  in  looking 
it  over,  and  will  take  pleasure  in 
commending  it  to  schools  consulting 
me  and  requiring  an  astronomy  of 
this  grade.  The  whole  series  of  As- 
tronomies reflects  credit  on  their 
distinguished  author  and  shows  that 
he  appreciates  the  needs  of  the 


Clarence  E.  Kelley,  Prin.  of  High 
School,  Haverhill,  Mass. :  It  seems 
to  me  the  book  is  admirably  adapted 
to  its  purpose,  and  that  it  accom- 
plishes the  difficult  task  of  present- 
ing to  the  student  or  reader  not 
conversant  with  Algebra  and  Geom- 
etry, an  excellent  selection  of  what 
may  with  profit  be  given  him  as  an 
introduction  to  the  science  of  astron- 


schools.  I  omy. 


NATURAL    SCIENCE.  109 

Blaisdell's  Physiofogies. 

By  ALBERT  F.  BLAISDELL,  M.D. 
The  Child's  Book  of  Health. 

Revised  Edition.  In  easy  lessons  for  schools.  Illustrated.  Moling 
price,  35  cents;  for  introduction,  30  cents. 

How  to  Keep  Well. 

Revised  Edition.  A  text-book  of  health  for  use  in  the  lower  grade  of 
schools.  Mailing  price,  55  cents ;  for  introduction,  45  cents. 

Our  Bodies  and  How  We  Live. 

Revised  Edition.  A  text-book  of  physiology  and  hygiene  adapted  for 
use  in  advanced  grammar  schools  and  high  schools.  12mo.  Cloth, 
vi  +  403  pages.  Mailing  price,  75  cents ;  for  introduction,  05  cents. 

How  to  Study  Physiology.  A  Handbook  for  Teachers.  25  cents. 
gLAISDELL'S  PHYSIOLOGIES  are  true,  scientific,  interesting, 
and  teachable.  The  matter  is  fresh  and  to  a  considerable 
extent  new.  The  language  is  clear,  terse,  and  suggestive.  Special 
emphasis  is  laid  upon  the  personal  care  of  health.  Reference  is 
made  throughout  the  series  to  the  evil  effects  of  stimulants  and 
narcotics  on  the  human  system. 

The  important  facts  in  "  How  to  Keep  Well  "  and  "  Our  Bodies  " 
are  illustrated  by  a  systematic  series  of  simple  experiments.  This 
feature  is  peculiar  to  the  Blaisdell  books  and  has  been  found  no 
less  valuable  than  original.  Endorsed  by  the  W.  C.  T.  U. 

A  Hygienic  Physiology. 

For  the  Use  of  Schools.  By  D.  F.  LINCOLN,  M.D.,  Author  of  School 
and  Industrial  Hygiene,  etc.  12mo.  Cloth.  Illustrated,  v  +  206 
pages.  Price  by  mail,  90  cents;  for  introduction,  80  cents. 

TT  is  the  distinctive  feature  of  this  book  to  put  hygiene  first  and 
make  anatomy  and  physiology  tributary,  instead  of   making 
anatomy  and  physiology  the  main  things  and  introducing  hygiene 
incidentally. 

An  Epitome  of  Anatomy,  Physiology,  and  Hy- 

giene.  —  Including  the  Effects  of  Alcohol  and  Tobacco. 

By  H.  H.  CULVER,  formerly  Teacher  of  Physiology  in  Bishop  College, 
Marshall,  Texas.  8vo.  Boards.^54^iggg&.By  mail,  25  cents;  for 
introduction,  20  cents.  A  concise,  tabular  view  of  the  whole  subject. 


'TTFI7BESIT7] 


/( 


UNIVERSITY  OP  CALIFORNIA  LIBRARY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


DEC  15  J9J5 


30m-l,'15 


YB   16919 


